Categories
Asia Noise News Environment

Noise in Malaysia

What Covid-19 did to Malaysia

2020 has been a year full of ups and downs. One big thing that affected, in fact, is still affecting the whole world is undeniably the Covid-19 pandemic. No doubt that the pandemic has caused a lot of downhills in the development of many aspects, like economy and social, but there is one thing that have shown obvious positive sign during this situation: the environmental change.

Figure 1 A picture showing the clearer skies in Kuala Lumpur, the capital of Malaysia (Photos: Filepic).

According to a Malaysian news report by Ming Teoh from The Star, the movement control order (MCO) that was carried out to tackle the Covid-19 spread in Malaysia has brought positive environmental impacts to the country (Teoh, 2020). People were amazed by the clean rivers, clear blue skies and the recovery of nature and wildlife. Of course, due to the MCO where a lot of human activities were restricted, the streets and urban roads have been very quiet as compared to the usual noise level. The improved noise quality resulted in lower noise pollution, which made the sounds of the fauna more apparent. But once everyone gets back to normal life when the MCO is lifted, how long can this positive environmental situation last? Will there be enough time for the environment to heal properly?

The Department of Environment (DOE), Ministry of Energy, Science, Technology, Environment and Climate Change (MESTECC), Malaysia

The Department of Environment (DOE) from the Ministry of Energy, Science, Technology, Environment and Climate Change (MESTECC) of Malaysia have been very concerned about this issue all the while, specifically on the noise quality of the country. They have constantly been updating the guidelines to handle noise or vibration for various applications, for example vehicle-noise, ambient noise, or outdoor noise sources in the environment. In one of the published guidelines for environmental noise limits and control (2009), the DOE have specified a table showing the permissible sound levels for different applications, shown in Table 1 as one of the examples from the guidelines (Air & Noise, 2019). 

Table 1 An example of the permissible sound levels listed in the guidelines published by the DOE.

The permissible sound levels differ by the applications (i.e. use of land, human density) and the different times of the day, to ensure that the circumstances of various conditions are taken into account during the sound level measurements. For instance, the ambient noise limits are set such that it is an absolute limit based on the average level of noise (which should not be exceeded in a specified period), or in accordance with a relative limit based on the permitted increase in noise level with respect to the background level. It is mentioned that the limits should always be consistent with the environmental noise climate of the location. The rest of the noise limit schedules listed in the guidelines include those for land use, road traffic, railway/transit trains, construction, and maintenance, which are the main sources of outdoor noise in the country. 

Besides that, the report also covers guidelines on planning process, noise impact assessments, quantifying of noise disturbance, and guidance in environmental noise mitigation through planning and control. These are ideally applied in new and existing projects planning, in which the projects can cover anything that involves noise, as a potential concern or needed to be measured and assessed. This is a very imperative measure from the DOE to enforce noise control in the country to work on controlling the noise impact of the relevant applications, thus overcoming the noise pollution in Malaysia. With these actions being taken and followed, the goal to maintaining a better noise quality in the country can be achieved in near future.

Written by:

Khei Yinn Seow

Mechanical Engineer

Geonoise Malaysia

khei@geonoise.asia 

References:

Air & Noise, P. S. C. S., 2019. Guidelines for Environmental Noise Limits and Control (Third Edition), Putrajaya: Department of Environment Malaysia.

Teoh, M., 2020. Blue skies, less waste: Covid-19 and the MCO’s effects on the environment., s.l.: The Star.

Categories
Asia Noise News Building Accoustics Environment Industrial

Noise Level Prediction in Industry (Oil & Gas, Power Generation, Process, etc.)

Most industrial activities create noise that can be harmful to the environment as well as to their workers. To minimize this effect, governments, associations, and companies have created regulations, standards, and codes to set the allowable noise both inside the sites, that can be harmful to the workers, as well as to the environment. In a lot of cases, during the planning phase, the plant owner and project management want to be sure that the noise levels are acceptable. Since the plant is not built yet, what can be done is creating a noise model to simulate the plant, so that the noise levels can be predicted. In this article, we will explore how we can do so.

The first thing we must know is how much noise does the noise sources inside of the plant will emit. The noise source is usually described in two ways which is Sound Power Level (Lw or SWL), and Sound Pressure Level (Lp or SPL) in certain distance, most commonly Lp in 1 m distance. There are multiple ways to get this information for certain noise sources. First, if the equipment type and model have been chosen, the equipment manufacturer will normally report the noise level in their datasheet. However, this is not usually the case with most of noise predictions since the noise study is normally done before the equipment suppliers are appointed. So, the second way to be able to predict the noise emission is by following empirical formulas that are developed by researchers. You can find such formulas in some textbooks, journals, and papers. For rotating parts, you will need its rated power and rotational speed to be able to estimate the noise emission. 

For example, in the speed range of 3000-3600 rpm, the noise level of a pump with drive motor power above 75 kW can be predicted using the following equation:

Suppose a pump with rotational speed of 3000 rpm and 100 kW, according to the formula, it can be estimated that the noise level at 1 m from the pump would be 92 dB. And suppose the noise source can be considered as point source on the ground (hemisphere propagation), the sound power level of the pump can be calculated using the following formula:

Where r is the distance from source to receiver

And in this case, the predicted Lw would be 100 dB.

Thirds, noise measurement to a similar equipment can also be an option to be able to determine the noise level of the new equipment. Another option, in some countries, there are noise emission limit for certain equipment, you can use that limit if it is applicable for your project.

After the Lw of all noise sources is obtained, we want to calculate the noise levels (the Lp) at the receivers. There are some standards which procedure can be followed to calculate this. Few of which are ISO 9613-2, NORD 2000, CNOSSOS EU, and many others. Most of the standards consider some factors to the calculation such as distance, atmospheric absorption, ground reflection, screening effect (from barriers and obstacles) and other factors such as volume absorption from vegetation, industrial site, etc. Most consultants and projects will require a software such as SoundPLAN to do this calculation.

Depending the project, there are few types of noise limit which compliance will need to be ensured. The most common ones are environmental noise limit, noise exposure limit, area noise limit and absolute noise limit. Besides, the noise level during emergency is also modelled so that the information can be used for safety and PAGA (Public Address and General Alarm) study.

Environmental noise limit is usually calculated for the plant’s contribution to the plant’s boundary as well as to the nearest sensitive receiver such as residential and school near the plant. How this is accessed depends on the regulation applicable on the plant area. In Indonesia for example, the noise limit for residential area is Lsm 55 dBA and industrial area is Lsm 70 dBA. Lsm is a measure like Ldn, but the night noise level addition is 5 dB instead of the 10 dB addition that most other countries, especially Europeans use. To ensure compliance with this regulation, the noise level at fence should be less than Lsm 70 dBA, and suppose there is a residential area nearby, the contribution from the site should be less than 55 dBA. It is also advisable to measure the existing noise level at the sensitive receivers to make the study more relevant to the situation. 

Noise exposure limit is the maximum exposure to noise that the workers get during their working period. In Indonesia, the noise exposure limit is 85 dBA for 8 working hours. To change the working hours, 3 dB exchange rate is used. For example, if the noise level in the plant is 88 dBA, then the workers can only work there for 4 hours, if it is 91 dBA, then the time limit is 2 hours, and so on. To extend the working hours on a noisy area, the options are to actually reduce the noise level by reducing the noise emission from the source or noise control at transmission (for example using barrier), or by usage of Hearing Protection Device (HPD) for the workers such as ear plugs and ear muffs. The noise exposure of workers after usage of HPD can be calculated using the following formula:

Where NRR is the noise reduction rating of the HPD in dB.

Different area might have different noise level limits, and therefore area noise limits are useful. For example, in an unmanned mechanical room, the noise level can be high, for instance 110 dBA. However, inside of the site office, the allowable noise level is much lower, for example 50 dBA. This noise level shall be calculated to ensure compliance with the noise limit. Different companies might have different limits for this to ensure their employees’ health and productivity. If the area is indoor and the noise source is outdoor, then the interior noise level can be estimated using standards such as ISO 12354-3. 

The absolute noise limit is the highest noise level allowable at the plant, and shall not be exceeded at any times, including emergency. In most cases, the absolute noise limit for impulsive sound is 140 dBA. To ensure compliance with this requirement, potential high-level noise shall be calculated, for example safety valves.

During emergency, different noise sources than normal situation will be activated, such as flare, blowdown valves, fire pumps, and other equipment. In such cases, the sound from the alarm and Public Address system must be able to be heard by the workers inside of the plant. Normally the target for the SPL from the PAGA system should be higher than 10 dB above the noise level. Therefore, the noise level during emergency in each area should be well-known. 

Written by:

Hizkia Natanael
Acoustic Engineer
Phone: +6221 5010 5025
Email: hizkia@geonoise.asia

Categories
Asia Noise News Building Accoustics Environment Industrial

Noise Level Prediction in Industry (Oil & Gas, Power Generation, Process, etc.)

Most industrial activities create noise that can be harmful to the environment as well as to their workers. To minimize this effect, governments, associations, and companies have created regulations, standards, and codes to set the allowable noise both inside the sites, that can be harmful to the workers, as well as to the environment. In a lot of cases, during the planning phase, the plant owner and project management want to be sure that the noise levels are acceptable. Since the plant is not built yet, what can be done is creating a noise model to simulate the plant, so that the noise levels can be predicted. In this article, we will explore how we can do so.

The first thing we must know is how much noise does the noise sources inside of the plant will emit. The noise source is usually described in two ways which is Sound Power Level (Lw or SWL), and Sound Pressure Level (Lp or SPL) in certain distance, most commonly Lp in 1 m distance. There are multiple ways to get this information for certain noise sources. First, if the equipment type and model have been chosen, the equipment manufacturer will normally report the noise level in their datasheet. However, this is not usually the case with most of noise predictions since the noise study is normally done before the equipment suppliers are appointed. So, the second way to be able to predict the noise emission is by following empirical formulas that are developed by researchers. You can find such formulas in some textbooks, journals, and papers. For rotating parts, you will need its rated power and rotational speed to be able to estimate the noise emission. 

For example, in the speed range of 3000-3600 rpm, the noise level of a pump with drive motor power above 75 kW can be predicted using the following equation:

Suppose a pump with rotational speed of 3000 rpm and 100 kW, according to the formula, it can be estimated that the noise level at 1 m from the pump would be 92 dB. And suppose the noise source can be considered as point source on the ground (hemisphere propagation), the sound power level of the pump can be calculated using the following formula:

Where r is the distance from source to receiver

And in this case, the predicted Lw would be 100 dB.

Thirds, noise measurement to a similar equipment can also be an option to be able to determine the noise level of the new equipment. Another option, in some countries, there are noise emission limit for certain equipment, you can use that limit if it is applicable for your project.

After the Lw of all noise sources is obtained, we want to calculate the noise levels (the Lp) at the receivers. There are some standards which procedure can be followed to calculate this. Few of which are ISO 9613-2, NORD 2000, CNOSSOS EU, and many others. Most of the standards consider some factors to the calculation such as distance, atmospheric absorption, ground reflection, screening effect (from barriers and obstacles) and other factors such as volume absorption from vegetation, industrial site, etc. Most consultants and projects will require a software such as SoundPLAN to do this calculation.

Depending the project, there are few types of noise limit which compliance will need to be ensured. The most common ones are environmental noise limit, noise exposure limit, area noise limit and absolute noise limit. Besides, the noise level during emergency is also modelled so that the information can be used for safety and PAGA (Public Address and General Alarm) study.

Environmental noise limit is usually calculated for the plant’s contribution to the plant’s boundary as well as to the nearest sensitive receiver such as residential and school near the plant. How this is accessed depends on the regulation applicable on the plant area. In Indonesia for example, the noise limit for residential area is Lsm 55 dBA and industrial area is Lsm 70 dBA. Lsm is a measure like Ldn, but the night noise level addition is 5 dB instead of the 10 dB addition that most other countries, especially Europeans use. To ensure compliance with this regulation, the noise level at fence should be less than Lsm 70 dBA, and suppose there is a residential area nearby, the contribution from the site should be less than 55 dBA. It is also advisable to measure the existing noise level at the sensitive receivers to make the study more relevant to the situation. 

Noise exposure limit is the maximum exposure to noise that the workers get during their working period. In Indonesia, the noise exposure limit is 85 dBA for 8 working hours. To change the working hours, 3 dB exchange rate is used. For example, if the noise level in the plant is 88 dBA, then the workers can only work there for 4 hours, if it is 91 dBA, then the time limit is 2 hours, and so on. To extend the working hours on a noisy area, the options are to actually reduce the noise level by reducing the noise emission from the source or noise control at transmission (for example using barrier), or by usage of Hearing Protection Device (HPD) for the workers such as ear plugs and ear muffs. The noise exposure of workers after usage of HPD can be calculated using the following formula:

Where NRR is the noise reduction rating of the HPD in dB.

Different area might have different noise level limits, and therefore area noise limits are useful. For example, in an unmanned mechanical room, the noise level can be high, for instance 110 dBA. However, inside of the site office, the allowable noise level is much lower, for example 50 dBA. This noise level shall be calculated to ensure compliance with the noise limit. Different companies might have different limits for this to ensure their employees’ health and productivity. If the area is indoor and the noise source is outdoor, then the interior noise level can be estimated using standards such as ISO 12354-3. 

The absolute noise limit is the highest noise level allowable at the plant, and shall not be exceeded at any times, including emergency. In most cases, the absolute noise limit for impulsive sound is 140 dBA. To ensure compliance with this requirement, potential high-level noise shall be calculated, for example safety valves.

During emergency, different noise sources than normal situation will be activated, such as flare, blowdown valves, fire pumps, and other equipment. In such cases, the sound from the alarm and Public Address system must be able to be heard by the workers inside of the plant. Normally the target for the SPL from the PAGA system should be higher than 10 dB above the noise level. Therefore, the noise level during emergency in each area should be well-known. 

Categories
Asia Noise News Building Accoustics Environment Industrial

Noise Level Prediction in Industry (Oil & Gas, Power Generation, Process, etc.)

Most industrial activities create noise that can be harmful to the environment as well as to their workers. To minimize this effect, governments, associations, and companies have created regulations, standards, and codes to set the allowable noise both inside the sites, that can be harmful to the workers, as well as to the environment. In a lot of cases, during the planning phase, the plant owner and project management want to be sure that the noise levels are acceptable. Since the plant is not built yet, what can be done is creating a noise model to simulate the plant, so that the noise levels can be predicted. In this article, we will explore how we can do so.

The first thing we must know is how much noise does the noise sources inside of the plant will emit. The noise source is usually described in two ways which is Sound Power Level (Lw or SWL), and Sound Pressure Level (Lp or SPL) in certain distance, most commonly Lp in 1 m distance. There are multiple ways to get this information for certain noise sources. First, if the equipment type and model have been chosen, the equipment manufacturer will normally report the noise level in their datasheet. However, this is not usually the case with most of noise predictions since the noise study is normally done before the equipment suppliers are appointed. So, the second way to be able to predict the noise emission is by following empirical formulas that are developed by researchers. You can find such formulas in some textbooks, journals, and papers. For rotating parts, you will need its rated power and rotational speed to be able to estimate the noise emission. 

For example, in the speed range of 3000-3600 rpm, the noise level of a pump with drive motor power above 75 kW can be predicted using the following equation:

Suppose a pump with rotational speed of 3000 rpm and 100 kW, according to the formula, it can be estimated that the noise level at 1 m from the pump would be 92 dB. And suppose the noise source can be considered as point source on the ground (hemisphere propagation), the sound power level of the pump can be calculated using the following formula:

Where r is the distance from source to receiver

And in this case, the predicted Lw would be 100 dB.

Thirds, noise measurement to a similar equipment can also be an option to be able to determine the noise level of the new equipment. Another option, in some countries, there are noise emission limit for certain equipment, you can use that limit if it is applicable for your project.

After the Lw of all noise sources is obtained, we want to calculate the noise levels (the Lp) at the receivers. There are some standards which procedure can be followed to calculate this. Few of which are ISO 9613-2, NORD 2000, CNOSSOS EU, and many others. Most of the standards consider some factors to the calculation such as distance, atmospheric absorption, ground reflection, screening effect (from barriers and obstacles) and other factors such as volume absorption from vegetation, industrial site, etc. Most consultants and projects will require a software such as SoundPLAN to do this calculation.

Depending the project, there are few types of noise limit which compliance will need to be ensured. The most common ones are environmental noise limit, noise exposure limit, area noise limit and absolute noise limit. Besides, the noise level during emergency is also modelled so that the information can be used for safety and PAGA (Public Address and General Alarm) study.

Environmental noise limit is usually calculated for the plant’s contribution to the plant’s boundary as well as to the nearest sensitive receiver such as residential and school near the plant. How this is accessed depends on the regulation applicable on the plant area. In Indonesia for example, the noise limit for residential area is Lsm 55 dBA and industrial area is Lsm 70 dBA. Lsm is a measure like Ldn, but the night noise level addition is 5 dB instead of the 10 dB addition that most other countries, especially Europeans use. To ensure compliance with this regulation, the noise level at fence should be less than Lsm 70 dBA, and suppose there is a residential area nearby, the contribution from the site should be less than 55 dBA. It is also advisable to measure the existing noise level at the sensitive receivers to make the study more relevant to the situation. 

Noise exposure limit is the maximum exposure to noise that the workers get during their working period. In Indonesia, the noise exposure limit is 85 dBA for 8 working hours. To change the working hours, 3 dB exchange rate is used. For example, if the noise level in the plant is 88 dBA, then the workers can only work there for 4 hours, if it is 91 dBA, then the time limit is 2 hours, and so on. To extend the working hours on a noisy area, the options are to actually reduce the noise level by reducing the noise emission from the source or noise control at transmission (for example using barrier), or by usage of Hearing Protection Device (HPD) for the workers such as ear plugs and ear muffs. The noise exposure of workers after usage of HPD can be calculated using the following formula:

Where NRR is the noise reduction rating of the HPD in dB.

Different area might have different noise level limits, and therefore area noise limits are useful. For example, in an unmanned mechanical room, the noise level can be high, for instance 110 dBA. However, inside of the site office, the allowable noise level is much lower, for example 50 dBA. This noise level shall be calculated to ensure compliance with the noise limit. Different companies might have different limits for this to ensure their employees’ health and productivity. If the area is indoor and the noise source is outdoor, then the interior noise level can be estimated using standards such as ISO 12354-3. 

The absolute noise limit is the highest noise level allowable at the plant, and shall not be exceeded at any times, including emergency. In most cases, the absolute noise limit for impulsive sound is 140 dBA. To ensure compliance with this requirement, potential high-level noise shall be calculated, for example safety valves.

During emergency, different noise sources than normal situation will be activated, such as flare, blowdown valves, fire pumps, and other equipment. In such cases, the sound from the alarm and Public Address system must be able to be heard by the workers inside of the plant. Normally the target for the SPL from the PAGA system should be higher than 10 dB above the noise level. Therefore, the noise level during emergency in each area should be well-known. 

Categories
Asia Noise News Building Accoustics Environment Industrial

Noise Level Prediction in Industry (Oil & Gas, Power Generation, Process, etc.)

Most industrial activities create noise that can be harmful to the environment as well as to their workers. To minimize this effect, governments, associations, and companies have created regulations, standards, and codes to set the allowable noise both inside the sites, that can be harmful to the workers, as well as to the environment. In a lot of cases, during the planning phase, the plant owner and project management want to be sure that the noise levels are acceptable. Since the plant is not built yet, what can be done is creating a noise model to simulate the plant, so that the noise levels can be predicted. In this article, we will explore how we can do so.

The first thing we must know is how much noise does the noise sources inside of the plant will emit. The noise source is usually described in two ways which is Sound Power Level (Lw or SWL), and Sound Pressure Level (Lp or SPL) in certain distance, most commonly Lp in 1 m distance. There are multiple ways to get this information for certain noise sources. First, if the equipment type and model have been chosen, the equipment manufacturer will normally report the noise level in their datasheet. However, this is not usually the case with most of noise predictions since the noise study is normally done before the equipment suppliers are appointed. So, the second way to be able to predict the noise emission is by following empirical formulas that are developed by researchers. You can find such formulas in some textbooks, journals, and papers. For rotating parts, you will need its rated power and rotational speed to be able to estimate the noise emission. 

For example, in the speed range of 3000-3600 rpm, the noise level of a pump with drive motor power above 75 kW can be predicted using the following equation:

Suppose a pump with rotational speed of 3000 rpm and 100 kW, according to the formula, it can be estimated that the noise level at 1 m from the pump would be 92 dB. And suppose the noise source can be considered as point source on the ground (hemisphere propagation), the sound power level of the pump can be calculated using the following formula:

Where r is the distance from source to receiver

And in this case, the predicted Lw would be 100 dB.

Thirds, noise measurement to a similar equipment can also be an option to be able to determine the noise level of the new equipment. Another option, in some countries, there are noise emission limit for certain equipment, you can use that limit if it is applicable for your project.

After the Lw of all noise sources is obtained, we want to calculate the noise levels (the Lp) at the receivers. There are some standards which procedure can be followed to calculate this. Few of which are ISO 9613-2, NORD 2000, CNOSSOS EU, and many others. Most of the standards consider some factors to the calculation such as distance, atmospheric absorption, ground reflection, screening effect (from barriers and obstacles) and other factors such as volume absorption from vegetation, industrial site, etc. Most consultants and projects will require a software such as SoundPLAN to do this calculation.

Depending the project, there are few types of noise limit which compliance will need to be ensured. The most common ones are environmental noise limit, noise exposure limit, area noise limit and absolute noise limit. Besides, the noise level during emergency is also modelled so that the information can be used for safety and PAGA (Public Address and General Alarm) study.

Environmental noise limit is usually calculated for the plant’s contribution to the plant’s boundary as well as to the nearest sensitive receiver such as residential and school near the plant. How this is accessed depends on the regulation applicable on the plant area. In Indonesia for example, the noise limit for residential area is Lsm 55 dBA and industrial area is Lsm 70 dBA. Lsm is a measure like Ldn, but the night noise level addition is 5 dB instead of the 10 dB addition that most other countries, especially Europeans use. To ensure compliance with this regulation, the noise level at fence should be less than Lsm 70 dBA, and suppose there is a residential area nearby, the contribution from the site should be less than 55 dBA. It is also advisable to measure the existing noise level at the sensitive receivers to make the study more relevant to the situation. 

Noise exposure limit is the maximum exposure to noise that the workers get during their working period. In Indonesia, the noise exposure limit is 85 dBA for 8 working hours. To change the working hours, 3 dB exchange rate is used. For example, if the noise level in the plant is 88 dBA, then the workers can only work there for 4 hours, if it is 91 dBA, then the time limit is 2 hours, and so on. To extend the working hours on a noisy area, the options are to actually reduce the noise level by reducing the noise emission from the source or noise control at transmission (for example using barrier), or by usage of Hearing Protection Device (HPD) for the workers such as ear plugs and ear muffs. The noise exposure of workers after usage of HPD can be calculated using the following formula:

Where NRR is the noise reduction rating of the HPD in dB.

Different area might have different noise level limits, and therefore area noise limits are useful. For example, in an unmanned mechanical room, the noise level can be high, for instance 110 dBA. However, inside of the site office, the allowable noise level is much lower, for example 50 dBA. This noise level shall be calculated to ensure compliance with the noise limit. Different companies might have different limits for this to ensure their employees’ health and productivity. If the area is indoor and the noise source is outdoor, then the interior noise level can be estimated using standards such as ISO 12354-3. 

The absolute noise limit is the highest noise level allowable at the plant, and shall not be exceeded at any times, including emergency. In most cases, the absolute noise limit for impulsive sound is 140 dBA. To ensure compliance with this requirement, potential high-level noise shall be calculated, for example safety valves.

During emergency, different noise sources than normal situation will be activated, such as flare, blowdown valves, fire pumps, and other equipment. In such cases, the sound from the alarm and Public Address system must be able to be heard by the workers inside of the plant. Normally the target for the SPL from the PAGA system should be higher than 10 dB above the noise level. Therefore, the noise level during emergency in each area should be well-known. 

Categories
Asia Noise News Building Accoustics Environment Industrial

Noise Level Prediction in Industry (Oil & Gas, Power Generation, Process, etc.)

Most industrial activities create noise that can be harmful to the environment as well as to their workers. To minimize this effect, governments, associations, and companies have created regulations, standards, and codes to set the allowable noise both inside the sites, that can be harmful to the workers, as well as to the environment. In a lot of cases, during the planning phase, the plant owner and project management want to be sure that the noise levels are acceptable. Since the plant is not built yet, what can be done is creating a noise model to simulate the plant, so that the noise levels can be predicted. In this article, we will explore how we can do so.

The first thing we must know is how much noise does the noise sources inside of the plant will emit. The noise source is usually described in two ways which is Sound Power Level (Lw or SWL), and Sound Pressure Level (Lp or SPL) in certain distance, most commonly Lp in 1 m distance. There are multiple ways to get this information for certain noise sources. First, if the equipment type and model have been chosen, the equipment manufacturer will normally report the noise level in their datasheet. However, this is not usually the case with most of noise predictions since the noise study is normally done before the equipment suppliers are appointed. So, the second way to be able to predict the noise emission is by following empirical formulas that are developed by researchers. You can find such formulas in some textbooks, journals, and papers. For rotating parts, you will need its rated power and rotational speed to be able to estimate the noise emission. 

For example, in the speed range of 3000-3600 rpm, the noise level of a pump with drive motor power above 75 kW can be predicted using the following equation:

Suppose a pump with rotational speed of 3000 rpm and 100 kW, according to the formula, it can be estimated that the noise level at 1 m from the pump would be 92 dB. And suppose the noise source can be considered as point source on the ground (hemisphere propagation), the sound power level of the pump can be calculated using the following formula:

Where r is the distance from source to receiver

And in this case, the predicted Lw would be 100 dB.

Thirds, noise measurement to a similar equipment can also be an option to be able to determine the noise level of the new equipment. Another option, in some countries, there are noise emission limit for certain equipment, you can use that limit if it is applicable for your project.

After the Lw of all noise sources is obtained, we want to calculate the noise levels (the Lp) at the receivers. There are some standards which procedure can be followed to calculate this. Few of which are ISO 9613-2, NORD 2000, CNOSSOS EU, and many others. Most of the standards consider some factors to the calculation such as distance, atmospheric absorption, ground reflection, screening effect (from barriers and obstacles) and other factors such as volume absorption from vegetation, industrial site, etc. Most consultants and projects will require a software such as SoundPLAN to do this calculation.

Depending the project, there are few types of noise limit which compliance will need to be ensured. The most common ones are environmental noise limit, noise exposure limit, area noise limit and absolute noise limit. Besides, the noise level during emergency is also modelled so that the information can be used for safety and PAGA (Public Address and General Alarm) study.

Environmental noise limit is usually calculated for the plant’s contribution to the plant’s boundary as well as to the nearest sensitive receiver such as residential and school near the plant. How this is accessed depends on the regulation applicable on the plant area. In Indonesia for example, the noise limit for residential area is Lsm 55 dBA and industrial area is Lsm 70 dBA. Lsm is a measure like Ldn, but the night noise level addition is 5 dB instead of the 10 dB addition that most other countries, especially Europeans use. To ensure compliance with this regulation, the noise level at fence should be less than Lsm 70 dBA, and suppose there is a residential area nearby, the contribution from the site should be less than 55 dBA. It is also advisable to measure the existing noise level at the sensitive receivers to make the study more relevant to the situation. 

Noise exposure limit is the maximum exposure to noise that the workers get during their working period. In Indonesia, the noise exposure limit is 85 dBA for 8 working hours. To change the working hours, 3 dB exchange rate is used. For example, if the noise level in the plant is 88 dBA, then the workers can only work there for 4 hours, if it is 91 dBA, then the time limit is 2 hours, and so on. To extend the working hours on a noisy area, the options are to actually reduce the noise level by reducing the noise emission from the source or noise control at transmission (for example using barrier), or by usage of Hearing Protection Device (HPD) for the workers such as ear plugs and ear muffs. The noise exposure of workers after usage of HPD can be calculated using the following formula:

Where NRR is the noise reduction rating of the HPD in dB.

Different area might have different noise level limits, and therefore area noise limits are useful. For example, in an unmanned mechanical room, the noise level can be high, for instance 110 dBA. However, inside of the site office, the allowable noise level is much lower, for example 50 dBA. This noise level shall be calculated to ensure compliance with the noise limit. Different companies might have different limits for this to ensure their employees’ health and productivity. If the area is indoor and the noise source is outdoor, then the interior noise level can be estimated using standards such as ISO 12354-3. 

The absolute noise limit is the highest noise level allowable at the plant, and shall not be exceeded at any times, including emergency. In most cases, the absolute noise limit for impulsive sound is 140 dBA. To ensure compliance with this requirement, potential high-level noise shall be calculated, for example safety valves.

During emergency, different noise sources than normal situation will be activated, such as flare, blowdown valves, fire pumps, and other equipment. In such cases, the sound from the alarm and Public Address system must be able to be heard by the workers inside of the plant. Normally the target for the SPL from the PAGA system should be higher than 10 dB above the noise level. Therefore, the noise level during emergency in each area should be well-known. 

Categories
Asia Noise News

Dogs Can Experience Hearing Loss

Just like humans, dogs are sometimes born with impaired hearing or experience hearing loss as a result of disease, inflammation, aging or exposure to noise. Dog owners and K-9 handlers ought to keep this in mind when adopting or caring for dogs, and when bringing them into noisy environments, says Dr. Kari Foss, a veterinary neurologist and professor of veterinary clinical medicine at the University of Illinois at Urbana-Champaign.

In a new report in the journal Topics in Companion Animal Medicine, Foss and her colleagues describe cases of hearing loss in three working dogs: a gundog, a sniffer dog and a police dog. One of the three had permanent hearing loss, one responded to treatment and the third did not return to the facility where it was originally diagnosed for follow-up care.

The case studies demonstrate that those who work with police or hunting dogs “should be aware of a dog’s proximity to gunfire and potentially consider hearing protection,” Foss said. Several types of hearing protection for dogs are available commercially.

Just as in humans, loud noises can harm the delicate structures of a dog’s middle and inner ear.

“Most commonly, noise-induced hearing loss results from damage to the hair cells in the cochlea that vibrate in response to sound waves,” Foss said. “However, extreme noise may also damage the eardrum and the small bones within the inner ear, called the ossicles.”

Pet owners or dog handlers tend to notice when an animal stops responding to sounds or commands. However, it is easy to miss the signs, especially in dogs with one or more canine companions, Foss said.

“In puppies with congenital deafness, signs may not be noticed until the puppy is removed from the litter,” she said.

Signs of hearing loss in dogs include failing to respond when called, sleeping through sounds that normally would rouse them, startling at loud noises that previously didn’t bother them, barking excessively or making unusual vocal sounds, Foss said. Dogs with deafness in one ear might respond to commands but could have difficulty locating the source of a sound.

If pet owners think their pet is experiencing hearing loss, they should have the animal assessed by a veterinarian, Foss said. Hearing loss that stems from ear infections, inflammation or polyps in the middle ear can be treated and, in many cases, resolved.

Hearing-impaired or deaf dogs may miss clues about potential threats in their surroundings, Foss said.

“They are vulnerable to undetected dangers such as motor vehicles or predators and therefore should be monitored when outside,” she said.

If the hearing loss is permanent, dog owners can find ways to adapt, Foss said.

“Owners can use eye contact, facial expressions and hand signals to communicate with their pets,” she said. “Treats, toy rewards and affection will keep dogs interested in their training.” Blinking lights can be used to signal a pet to come inside.

Hearing loss does not appear to affect dogs’ quality of life, Foss said.”A dog with congenital hearing loss grows up completely unaware that they are any different from other dogs,” she said. “Dogs that lose their hearing later in life may be more acutely aware of their hearing loss, but they adapt quite well. A dog’s life would be significantly more affected by the loss of smell than by a loss of hearing.”

Written by:

Pitupong Sarapho (Pond)
Acoustical Engineer

Geonoise (Thailand) Co., Ltd.
Tel: +6621214399
Mobile: +66868961299
Email: pond@geonoise.asia

Credit: Diana Yates, University of Illinois at Urbana-Champaign

Categories
Asia Noise News Building Accoustics

Railway Noise

Rail transport or train transport is one of the main transportation modes these days, both for transferring passengers and goods. Every day people commute to work and back home using trains in a form of subway systems, light rail transits and other types of rail transport. These types of system can create noise both to the passengers inside of the train as well as to the environment. In this article, we will discuss about noise source components that we hear daily both inside and outside of the train.

If we pay attention to the noise when we are on board of a train, there are more than one noise source that we can hear. The main sources for interior noise in a train are turbulent boundary layer, air conditioning noise, engine/auxiliary equipment, rolling noise and aerodynamic noise from bogie, as illustrated in the following figure.

By the way, we wrote and recorded the sound of Jakarta MRT. You can see the link below to help you imagine the train situation better.

Exploring Jakartan Public Transportation Through The Sound

Rolling noise is caused by wheel and rail vibrations induced at the wheel/rain contact and is one of the most important components in railway noise. This type of noise depends on both wheel and rail’s roughness. The rougher the surface of both components will create higher noise level both inside and outside of the train. To be able to estimate the airborne component from the rolling noise, we must consider wheel and track characteristics and roughness.

Another noise component that contributes a lot to railway noise is aerodynamic noise which can be caused by more than one sources. These types of sources may contribute differently to internal noise and external noise. For example, aerodynamic noise contributes quite significantly at lower speeds to internal noise while for external noise, it doesn’t contribute as much if the train speed is relatively low. For example, on the report written by Federal Railroad Administration (US Department of Transportation), it is stated that aerodynamic sources start to generate significant noise at speeds of approximately 180 mph (around 290 km/h). Below that speed, only rolling noise and propulsion/machinery noise is taken into consideration for external noise calculation. In addition to external noise, machinery noise also contributes to the interior noise levels. This category includes engines, electric motors, air-conditioning equipment, and so on. 

To perform the measurements of railway noise, there are several procedures that are commonly followed. For measurement of train pass-by noise, ISO 3095 Acoustics – Railway applications – measurement of noise emitted by rail bound vehicles, is commonly used. This standard has 3 editions with the first published in 1975, and then modified and approved in 2005 and again in 2013. The commonly used measures for train pass-by are Maximum Level (LAmax), Sound Exposure Level (SEL) and Transit Exposure Level (TEL).

For interior noise, the commonly used test procedure is specified in ISO 3381 Railway applications – Acoustics – Measurement of noise inside rail bound vehicles. This procedure specifies measurements in few different conditions such as measurement on trains with constant speed, accelerating trains from standstill, decelerating vehicles, and stationary vehicles. 

Written by:

Hizkia Natanael

Acoustical Design Engineer

Geonoise Indonesia

hizkia@geonoise.asia

Reference:

D. J. Thompson. Railway noise and vibration: mechanisms, modelling and means of control. Elsevier, Amsterdam, 2008

Federal Railroad Administration – U.S. Department of Transportation, High-Speed Ground Transportation Noise and Vibration Impact Assessment. DOT/FRA/ORD-12/15. 2012

Categories
Asia Noise News

How Sound Wave Work Underwater?

Do You Know?

Acoustics is not only about sound propagation in the air, but also its propagation in the water. The study of sound propagation and how it behaves in water is called underwater acoustics. Underwater acoustics is a branch of science, and it has become a technology that has been used since World War I. Even before that, in 1490, Leonardo da Vinci has stated his theory in an article “if you stop your ship in the ocean and you put one side of a long tube into the water, then put your ear in the other side, you’ll listen the sound of the ship from great distance.” This indicates that underwater acoustics technology is already known for long time. 

In World War II, in military cases, underwater acoustics was used as a communication platform to channel information through the water. In 1925, underwater acoustics was used to measure ocean depth based on sound waves obtained — one of its usability is to find the plane crashed into the bottom of the sea. Time went by and many technologies developed and researches were performed.

One of the applications which can also be used for fisherman is fish-finder navigation tools. These tools can be used for fishers to find schools of fish in the ocean. We can also know the distance and the position of the school of fish from the ship based on the frequency range of the sound propagated.

In the industry, underwater acoustics has been applied to determine the presence of oil and gas in the sea. The method used is quite effective and efficient. In disaster management, early detection of a tsunami from the sea has been developed based on the propagation of infrasound detected from the seabed. In recent years, one technology that has attracted interest in many studies is the Autonomous Underwater Vehicle (AUV). AUV is an unmanned underwater vehicle, where the AUV can identify underwater biology and physics. The use of AUV can be the best choice in identifying the shape conditions of coastal waters because it can be operated in the long run. Besides, the use of AUV can also avoid damage to coral reefs and marine ecosystems.

The necessity for underwater research is quite high, especially for countries with vast oceans, such as Indonesia. Underwater acoustic research is needed in mining operations, observations on coral reefs, offshore oil exploration, and sea accidents.

The speed of a wave is the rate at which vibrations move through the medium. Sound moves at a faster pace in water and with long-distance than in air because the mechanical properties of water differ from the air. We know that the speed of sound wave propagation in the air is between 333 m/s and 340 m/s, the speed of sound waves in water is four times faster than the speed of sound in the air. The speed of sound waves in water ranges from 1500 m/s to 1520 m/s. We know that sound propagation occurs because of the ups and downs of particles in a medium. At sea, the deeper the depth of the sea, the higher the pressure. High-pressure water particles will be compressed so that they continue to propagate the sound without losing much energy. Besides, the density in water is higher than the density in the air. This causes the sound can travel fast and far away in the water. Unfortunately, the speed of sound in seawater is not a constant value. It varies by a small amount (a few percent) from place to place, season to season, morning to evening, and with water depth. Although the variations in the speed of sound are not large, they have important effects on how sound travels in the ocean. However, the temperature in seawater also affects the speed of sound waves, warm water travels faster and farther than colder water. 

There are three layers in the sea, based on its temperature, namely mixed water, thermocline, and deep water. In the thermocline, temperature decreases rapidly from the mixed upper layer of the ocean to much colder deep water. In the thermocline, the speed of sound waves decreases with the depth of the sea. In the layer below the thermocline, the temperature becomes constant again, and the pressure increases. In this layer, the speed of the sound waves again increases with the depth of the sea.

Temperature ⇢

As we know, wavelength is inversely proportional to frequency.

As can be seen in the equation above, the lower the frequency the longer the wavelength. Therefore, a 20 Hz sound wave is 75 m long in the water whereas a 20 Hz sound wave in air is only 17 m long in the air. Generally, the sensor used to capture underwater sound is a hydrophone or underwater microphone.

Decibels as a unit of sound pressure is the ratio between the pressure measurement and the reference pressure. Note that the reference pressure in the air with water is different. Therefore, 150 dB of sound in water is not the same as 150 dB of sound in air. In air, the reference pressure is 20μPa while in water the reference pressure is 1μPa. Based on the Sound Pressure Level equation, the conversion value of dB in air to water is

The characteristic impedance of water is about 3600 times that of air then

Therefore, the air to water conversion factor is

For example, if the sound of a jet engine in the air is 135 dB then the water is 197 dB in water.

Written by:

Adetia Alfadenata

Acoustic Engineer

Geonoise Indonesia

support.id@geonoise.asia

Reference:

  • Urick, Robert J.1983.” Principal of Underwater Sound/3rd Edition”.McGraw-Hill Book Company
  • Nieukirk, Sharon.” Understandig Ocean Acoustic”.NOAA Ocean explorer Webmaster
  • Singh H, Roman C, Pizarro O, Eustice R. Advances in High Resolution Imaging from Underwater Vehicles. In: Thrun S, Brooks R, Durrant-Whyte H, editors. Robotics Research. vol. 28 of Springer Tracts in Advanced Robotics. Springer Berlin Heidelberg; 2007. p. 430–448
  • Pike, John.  “Underwater Acoustic”. Diakses secara online melalui https://fas.org/man/dod-101/sys/ship/acoustics.htm
  • Discovery of Sound in the Sea.”How does sound in air differ from sound in water?” diakses secara online melalui https://dosits.org/science/sounds-in-the-sea/how-does-sound-in-air-differ-from-sound-in-water/
Categories
Asia Noise News

Noise, Nuisance or Danger

As an introduction to this question some basic facts about noise.

Basic noise facts

Noise is typically defined as ‘unwanted sound’. The unit for sound is the Decibel which is a value calculated with logarithms from the pressure to get a scale from 0 to 120 dB where 0 dB is the hearing threshold for a young person with healthy hearing and 120 dB is the pain threshold.

We can state that noise is a type of energy created by vibrations. When an object vibrates it causes moment in air particles. The particles will bump into each other and will generate sound waves, they are ongoing until they run out of energy.

High and low tones are perceived by our hearing due to fast and slow vibrations.

Sound needs a medium to travel and the speed of sound is around 340 meter per second. Examples of typical noise levels:

Due to the nature of the calculation of Decibels we cannot just add them together.

Examples:

3 dB + 3 dB = 6 dB

But…..

10 dB + 10 dB is not 20 dB but 13 dB

The Decibel (sound pressure level) for sound in air is relative to 20 micro pascals (μPa) = 2×10−5 Pa, the quietest sound a human can hear.

The human hearing system

The human hearing system is capable of hearing sounds between 20 Hz and 20000 Hz. Below 20 Hz is called infra sound and above 20000 Hz is called ultrasounds. Both infra- and ultrasound is not audible for us. Elephants however can hear frequencies as low as 14 Hz and bats can hear frequencies up to 80000 Hz.

A special noise weighting for the human perception has been introduced in the 1930’s and called the A-weighted Decibel, dB(A). This was introduced to align the noise levels with the sensitivity and physical shape of the human hearing system.

Basic human hearing system

When sound waves enter the ear, they travel up the ear canal and hit the ear drum, the ear drum will vibrate and the three smallest bones in the human body will transfer these vibrations to the fluid in our inner ear’s sensory organ the cochlea. The sensory hair cells will vibrate which will send nerve impulses to the brain, the brain will translate these impulses for us and we perceive sound!

Dangers of noise

Noise from certain music can be a very pleasurable sound for one person and a horrific noise for another. From this fact we can see that noise is not only an absolute value but also strongly depending on the receiver’s mindset.

However, there are some clear absolute values concerning the danger levels of noise.

  • Generally accepted as safe is spending 8 hours per day in an environment not exceeding 80 dB(A)
  • NOT safe would be to spend 1 hour in a disco with levels at 100 dB(A) which are easily exceed nowadays

Apart from the obvious hearing loss there are many other issues that can arise from exposure to (too) high noise levels such as:

  • Hypertension
  • Heart disease
  • Annoyance – stress
  • Immune system – psychosomatic

The positive side to remember is that Noise Induced hearing loss is 100% preventable!!

Worldwide solutions

Governments (especially in Europe) know the actual cost of high noise exposure and they concluded that protecting their citizens from high noise exposure (during working hours, recreation as well as during sleep) is far more effective than dealing with the costs of citizens enduring high noise related illnesses, demotivation, sleep disturbance etc.

They are investing in quiet schools (optimal learning environment), quiet hospitals (patients recover a lot faster in quiet wards), implement city planning to create quite zones.

Of course, they also have strong noise regulations that are being enforced.

Acoustical societies worldwide help to create awareness and leverage noise legislations with governments.

Noise in Asia

I have been living in Asia for the last 15 years and of course I noticed it’s noisy. Noise regulations (if exist at all) are very lenient and mostly not enforced. I’m very happy to see that Acoustical Societies are coming up in Asian countries and can convince governments to invest in setting up proper noise regulations and enforcing them. I’m very happy to be able to contribute to a quieter world by creating more awareness for the dangers of noise!