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Noise Pollution and Cardiovascular Diseases: A Growing Concern

Noise Pollution and Cardiovascular Diseases: A Growing Concern
Noise Pollution and Cardiovascular Diseases: A Growing Concern

Noise pollution is a growing problem in our modern world. It is the unwanted or excessive sound that can have negative effects on human health and well-being. In recent years, researchers have found that noise pollution can be linked to various health problems, including cardiovascular diseases.

A study conducted by the World Health Organization (WHO) showed that exposure to environmental noise can have adverse effects on public health. According to the WHO, more than one billion people around the world are exposed to high levels of noise, and this exposure can lead to a range of health problems, including cardiovascular diseases.

Cardiovascular diseases are the leading cause of death globally, accounting for nearly 18 million deaths each year. These diseases affect the heart and blood vessels and can result in heart attacks, strokes, and other health complications.

The link between noise pollution and cardiovascular diseases has been established through numerous studies. One of the most significant studies in this regard was conducted by the University of Oxford. In this study, researchers found that exposure to high levels of noise can increase the risk of heart disease by up to 50%. The study also found that noise pollution can increase the risk of stroke and other cardiovascular diseases.

So, how does noise pollution affect the cardiovascular system? The answer lies in the stress response of the body. When we are exposed to noise, our body reacts by releasing stress hormones like cortisol and adrenaline. These hormones trigger the “fight or flight” response, which can cause an increase in heart rate, blood pressure, and breathing rate. This response is normal and evolutionarily adapted to help us deal with threats and danger. However, chronic exposure to environmental noise can lead to prolonged stress response, leading to long-term damage to the cardiovascular system.

Environmental noise can also disrupt sleep, which is essential for the proper functioning of the cardiovascular system. Lack of sleep can lead to high blood pressure, impaired glucose tolerance, and other negative impacts on the heart and blood vessels.

Moreover, the impact of noise pollution on the cardiovascular system is not limited to adults. Children who grow up in noisy environments may be at higher risk of developing cardiovascular diseases later in life. Studies have shown that children exposed to high levels of traffic noise are more likely to have high blood pressure, even at a young age. This is particularly concerning, as high blood pressure in childhood can lead to a higher risk of developing cardiovascular diseases in adulthood.

It is important to note that noise pollution is not just limited to traffic noise. It can also come from sources like aircraft, industrial activity, and even household appliances. Therefore, it is crucial to take steps to reduce noise pollution in our environment. Governments around the world are taking measures to reduce noise levels, such as creating noise barriers, regulating noise emissions from industrial activity, and restricting nighttime transport.

Individuals can also take steps to reduce their exposure to noise pollution. This can include wearing earplugs or noise-canceling headphones, avoiding noisy environments, and choosing quieter modes of transportation. In addition, creating a quiet environment at home, such as using soundproof curtains or adding insulation, can also help reduce noise levels.

In conclusion, noise pollution is a significant public health concern that can have negative effects on the cardiovascular system. Chronic exposure to environmental noise can lead to a range of health problems, including heart disease, stroke, and high blood pressure. It is crucial to take steps to reduce noise pollution in our environment and to raise awareness about the importance of protecting our health from the harmful effects of noise pollution.

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Songkran Celebration – Noise complaints during holidays

Songkran Celebration – Noise complaints during holidays
Songkran Celebration – Noise complaints during holidays

Punyakorn, April 2023

Geonoise (Thailand) Co., Ltd

The previous week is a week of celebration in Thailand for the Thai New Year or also known as “Songkran Days”. The celebration usually lasts for three days from 13 -15 April every year. This celebration is also well known for the way people celebrate by adapting the traditional activity to a water festival or water fights. This year is also a little bit special after the government put on a break during the COVID-19 situation. There is much positive feedback from the people that finally things tend to turn back to the normal conditions that they can celebrate, and many festivals are now allowed again.

There are many well-known areas or streets where most Thai and foreigners go to enjoy the festival and the water fights, but some might not be so convenient to travel across the city there. That’s when people need to find their way of celebrating!

Many clips on the internet show how people are having fun at their own houses, most people will have a small water station in front of their home where their neighbors can join when they are passing by. Some might make it bigger and more fun, having loudspeakers and playing some partying music.

However, this might be the start of the complaints….

What makes party music might be a disturbance more than a fun to the neighbor?

Party music is made to make people feel fun and enjoying. That is why most party music contains a lot of heavy beats and low bass sounds. These sounds are called ‘low frequency’ in a more engineering way. Normally we are not good at hearing these low frequency, but our ears are smart, it detects these low frequency a lot better when the sound is loud enough and when it plays in beat (or called ‘impulse’ by engineers). These low frequencies are also good at traveling long distances and having big waveform, this makes low frequency can pass through a wall without taking so much effort!

What should we do to prevent complaints?

If you’re planning to have a party again next year with some music in the backyard, you might try to keep the volume a bit lower and not boost the bass of your speakers. Second, be careful about your party time, after 10 pm is commonly known as nighttime when people need to rest, they are more sensitive to noise during this time. There are laws and regulations from the government protecting people’s health, so the laws are more sensitive during this time of day as well. Third, a small party room in your home is also a good idea! These days there are several companies that can help you with the design of a soundproof room with a good sound system.

What should I do if my neighbors are making noise?

Keep in mind that the laws are protecting you! You might try to contact the police officer in your area and not engage the neighbor by yourself. The police can help stop the noisy activity. Another regulation is by the Department of Public Health of Thailand, contact your local authorities to stop the disturbance activity. The laws protect your right to have good health and proper rest.

Thai Ministry of Justice provided an infographic for the related laws that emitting loud noise and creating disturbance can lead to a fine from 1,000 baht – 10,000 baht or imprison not exceeding 1 month (depending on the law section).

Follow this link: https://www.moj.go.th/view/75639

Prevent noise in the long run: interested in improving your home acoustic insulation?

You may need a professional acoustic consultant to find the most effective way, especially when you are dealing with low-frequency noise. This noise is really good at traveling through structure, normal designs or materials might not work at their best performance without proper acoustic designs.

Celebrating Songkran in Thailand next year?

Feels the fun and enjoy the festival for three days long here in Thailand.
But after this, you might want to keep in mind and care for others who might not celebrate the festival as well.

Happy Songkran Days!

References

Department of Health, Ministry of Pubic Health (2560). พระราชบัญญัติการสาธารณสุข พ.ศ. 2535 หมวด 5.

กฎหมายน่ารู้ ตอนที่ 388 : เพื่อนบ้านทำเสียงดังเดือดร้อนรำคาญ เสี่ยงคุก 1 เดือน ปรับ 1 หมื่น. (2022, September 28). Retrieved from MINISTRY OF JUSTICE OF THAILAND: https://www.moj.go.th/view/75639

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Asia Noise News Building Accoustics Environment Uncategorized

Importance of acoustics in office space

office space acoustics

Office – traditionally known as a place for work, means more than just that in this modern era. Today, apart from being used for conventional office activities like reading, writing, or computer works, office is also the space for open innovative discussions, private meetings, business collaborations and a venue for office members to connect and build strong peer relationships. Certain offices even provide a space for entertainment purpose so that employees can have fun to destress from work.

Notice the connections between all the activities that can happen in the office? Each of them involves different levels and types of noise. This is when office acoustics comes into the picture.

Investing into the acoustics design of office spaces can be more important than what you may think it should be. High noise levels in the office have been one of the main complaints among employees, as it can significantly affect their work performance and productivity. Noise can come from the activities like keyboard-clicking, printing noise, or low frequency hums from office equipment like printers or computers. With high noises, conversations in the office will be difficult, such that employees will end up having to raise their voice while talking – eventually making things worse.

It is therefore imperative to focus on the office acoustics, especially for the following:

  1. Effective communication

Having the background noise under controlled in a office will ensure speech clarity during conversations, be it among employees, or when talking to clients.

  1. Employees’ wellbeing

Long exposure to high noise will cause increase in both physical and psychological stress levels among employees, leading to poorer productivity and communication. Prolonged stress can possibly cause harmful health effects, such as headache, high blood pressure, or increase in heart rate etc.

  1. Privacy

It is often required to have one-to-one meetings for highly confidential topics in the office, hence it is important to have spaces that offer sufficient privacy to prevent conversations cannot be overheard.

  1. Work performances

As mentioned in point 2 as well, noisy environments will cause interruptions during work, leading to difficulties in focusing on work. This will thus influence the employees’ wellbeing, linking back to point 2.

Now that the importance of office acoustics have been known, are there any ways to treat the noisy office environment, or even better…avoid it?

The acoustic quality of an office, or room in general, can be determined by doing reverberation time (RT) measurements. RT is defined by the time taken for reverberation to decay, where typically shorter RT is preferred for better speech intelligibility, as there will be less reverberation, or in layman terms “echo” that exists in the room. High reverberation is normally due to the hard structural surfaces that offices are built with, such as concrete, glass, plaster etc. To reduce the RT, it is recommended to install sound absorbing materials like acoustic ceilings, acoustic wall panels, thicker carpets/curtains or other similar products in the office. The absorption performances of these products can be defined by finding out the sound absorption coefficients (α) of the material, which should be already stated in the datasheets by manufacturers. Sound absorption is relatable to sound reflections of a room.

Reverberation control can then influence the speech intelligibility of a room, which can be measured as the Speech Transmission Index (STI), or speech to noise ratio (SNR). The higher the SNR or STI, the better the speech intelligibility. According to the rule of thumb, SNR should be essentially at least 10-15 dB for good speech intelligibility, which means that the speech should ideally be 10-15 dB above the background noise to be clearly heard. However, to meet the goal for privacy, it should be the other way round, where SNR should be as low as possible.

On the other hand, sound insulation, sometimes known as attenuation, associates with the sound transmission control between adjacent rooms. The purpose of having sound insulation is to achieve better privacy by effectively blocking noise travelling from one room to another. Similar to sound absorption, sound insulation of a product can be graded using a single figure rating called Sound Reduction Index (R). Sound transmission can happen when sound passes through structures like partitions/walls/floors/ceilings. Sound can also transmit through hollow elements in the building like ventilations, ducts, pipes, claddings etc. Therefore, it is important to design the interior carefully and ensure that the construction of the building is done properly to avoid any unnecessary costs for remedial work in the future.

As much as the interior aesthetic of office space should be the key of design, acoustics should not be neglected as well, because it will strongly affect the users’ experience while working or carrying out tasks in the office space. In fact, with the variety of acoustic treatment products available in today’s market, it is definitely possible for both aesthetic and acoustics to be taken care of without sacrificing either, especially when interior designers often can work with acoustic consultants nowadays. Hence, do consider to put in more effort in the soundscape design of your workspace, for the better wellbeing of both you and your fellow workmates.

 

REFERENCES:

https://www.barbourproductsearch.info/FIS-Acoustic-Guide-2015-file100897.pdf

https://www.workspacedesign.co.uk/

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Control Valves Noise

The noise generated by control valves is a result of the turbulent flow of fluid through the valve and the pressure drop across the valve. As the fluid passes through the valve, it experiences sudden changes in direction and velocity, which can create turbulence and vortices that generate noise.

When the pressure of the liquid flowing through the valve drops below its vapor pressure, bubbles can form and collapse rapidly, creating shock waves that generate noise. This formation and collapse of vapor bubbles in a flowing liquid is called cavitation.

The severity of cavitation noise depends on several factors, including the pressure drop across the valve, the fluid properties (such as density and viscosity), and the valve design. Some common methods to reduce control valve cavitation noise include:

Increasing the pressure drop across the valve: This can be done by installing a pressure-reducing valve upstream of the control valve. By reducing the pressure upstream of the valve, the pressure drop across the valve is reduced, which can reduce the likelihood of cavitation.

  1. Increasing the valve size: A larger valve size can reduce the velocity of the fluid flowing through the valve, which can reduce the likelihood of cavitation.
  2. Using a different valve trim: The valve trim is the internal components of the valve that come into contact with the fluid.
  3. Using a different trim design, such as a multistage trim or a cage-guided trim, can reduce the likelihood of cavitation.
  4. Using a different valve material: Some valve materials, such as hardened steel, can be more resistant to cavitation than others.
  5. Adding a noise-reducing insert: A noise-reducing insert, such as a diffuser or an orifice plate, can be installed downstream of the valve to reduce the noise generated by cavitation.

It is important to note that while these methods can reduce the severity of cavitation noise, they may not eliminate it entirely. In some cases, additional noise mitigation measures may be necessary, such as installing a sound barrier or using ear protection.

The noise generated by control valves can be problematic for a number of reasons. For example, excessive noise can be a nuisance for workers or occupants in a facility, and it can even be a safety hazard if it interferes with communication or causes distraction. Noise can also be damaging to equipment and structures if it causes vibrations or resonance.

The noise level of control valves can be calculated using several methods, including empirical equations, computational fluid dynamics (CFD) simulations, and experimental measurements. Here are some common methods:

  1. Empirical Equations: Empirical equations are mathematical formulas that relate the noise level of a control valve to its flow rate and pressure drop. One such equation is the Masoneilan-Kates equation, which is commonly used in the industry. This equation is:

Lp = K1 + K2 * log10(Q) + K3 * log10(P1-P2) + K4 * log10(Q) * log10(P1-P2)

where Lp is the sound pressure level in decibels (dB), Q is the volumetric flow rate in cubic meters per hour (m3/h), P1 is the upstream pressure in kilopascals (kPa), and P2 is the downstream pressure in kPa. K1, K2, K3, and K4 are constants that depend on the valve size, type, and characteristics.

  1. Computational Fluid Dynamics (CFD) Simulations: CFD simulations use computer software to model the flow of fluids through a control valve and predict the resulting noise level. These simulations can provide detailed information about the flow patterns and turbulence that cause noise. However, CFD simulations require significant computational resources and expertise to perform.

 

  1. Experimental Measurements: Experimental measurements involve installing a control valve in a test rig and measuring the noise level using a sound level meter. This method provides direct, accurate measurements of the noise level but may be time-consuming and expensive.

Overall, the choice of method depends on the accuracy required, the resources available, and the expertise of the user.

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Noise complaints lead to drug bust in Thailand

noise complaints lead to drug bust Thailand
noise complaints lead to drug bust Thailand

You can make some noise, or you can break some laws, but you should avoid doing both. After neighbours complained of a Pathum Thani condo in a luxury building making excessive noise, police checked it out and uncovered a drug-dealing operation. The investigation led to several arrests.

The Department Of Provincial Administration joined the district chief of Klong Luang in Pathum Thani to investigate the noise complaint and ended up setting up a sting operation that culminated in a drug bust instead of just a noise violation.

noise complaints lead to drug bust Thailand
noise complaints lead to drug bust Thailand

The sting offered a low-level drug deal of just 500 baht and ensnared a 26-year-old Thai man and a 24-year-old Thai man who was a fourth-year university student. The Pathum Thani bust recovered the 500 baht from the drug deal as well as 2 full marijuana plants and imported heads for growing, weighing just over 46 grams. Other paraphernalia and evidence was seized too.

The raid was a small one, but police leveraged the young dealers to try to climb up the supply chain for a more significant bust. The 2 small-time dealers rolled over on another location in Pathum Thani just a few kilometres where police encountered 4 people doing drugs.

Police found and seized 514 grams of compressed marijuana on the premise in the second bust. They also made 2 more arrests related to the case including following the trail from the busts to locate and arrest a drug runner who was stopped in the middle of a delivery. He had 182 grams of marijuana on him.

The man claimed that he had no idea that the parcels he was delivering contained illegal drugs, saying that a woman who looked like a normal vendor told him he was just delivering cakes, for which he was paid a mere 280 baht.

Source

 

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Regulations, guidelines, and standards regarding environmental noise in Indonesia

With all the development, industrial activities and community activities in Indonesia, noise has become one of the problems that arises in some places in Indonesia. Indonesia already has some regulations, guidelines, and standards to safeguard the noise levels. This is important mainly to support a healthy environment for the people, and also to improve budgeting certainty of projects that will produce noise during their operations.

The following are the regulations, standards and guidelines related with environmental noise in Indonesia.

Environmental Noise Regulations

Regulations regarding environmental noise generally can be categorized into two types which are emission regulation and immission regulation. Emission regulations regulate how much noise can a noise source produces noise, while immission regulation regulates how much noise can a receiver or area receives noise.

Examples of noise emission regulations in Indonesia are:

  • Decree of Minister of Environment and Forestry No. 56 year 2019 (P.56/MENLHK/SETJEN/KUM.1/10/2019) regarding noise limits of new types of motorized vehicles and in production M category, N category, and L category.
  • Decree of Minister of Transportation of Republic of Indonesia No. PM 62, year 2021 regarding civil aviation safety section 36 regarding noise standard dan type certification and aircraft airworthiness

The two ministerial decrees above regulate how much noise can be produced by vehicles that are used on road and aircraft that can operate within Indonesian territory.

The regulation that regulates environmental noise level at the receiver is:

  • Decree of Minister of Environment No. 48 year 1996 about noise level limits

 

The decree states the noise limits that are allowed for the receiver according to its function – for example for residential area, the noise limit is 55 dBA and for industrial area 70 dBA. More details on the following link: https://www.konsultasi-akustik.com/en/environmental-noise-measurement/

 

Beside the regulations above, there are other requirement such as one written on Government Regulation (PP) No. 36 year 2005 regarding implementation rules of the Law No. 28 year 2002 regarding buildings. One of the points require noise reduction means for toll roads in residential area or existing city centers.

 

Guidelines regarding Environmental Noise

 

Beside the regulation, there are some technical guidelines that are written by Ministry of Public Works as follows:

  • Technical guidelines Ditjen Bina Marga No. 36 year 1999: Noise barrier planning guidelines
    In these guidelines, criteria to categorize area as safe, moderate and high risk are given. Moreover, the guidelines also state measurement techniques for measurement beside road and common type, shape and material of noise barriers.
  • Construction and building guidelines Pd T-10-2004-B: Road traffic noise prediction.

These guidelines adopt calculations from Calculation of Road Traffic Noise (CoRTN, UK, 1998) which contain noise calculation method based on traffic volume and speed. There are also corrections for heavy vehicle percentage, speed, gradient and road surface. From this calculation, propagation to receiver can be calculated considering distance, screening, reflection and angle of view.

  • Construction and building guidelines Pd T-16-2005-B: Mitigation of road traffic noise

The guidelines lay out methods to mitigate noise from traffic which is based on measurement (which are written on Permen LH No. 48 year 1996 and guidelines No.36 year 1999 above) and can also be based on predictions (Following construction and building guidelines Pd T-10-2004-B)

 

Environmental Noise Standards

 

Beside the regulations and guidelines, there are Indonesian National Standard (SNI) document that are written by National Standardization Body (BSN) that are related to environmental noise:

  • SNI 19-6878-2002 – Road traffic noise test L10 and Leq
    This standard contains test method which state testing procedure and data processing steps to calculate LA to L10 and Leq
  • SNI 8427:2017 – Pengukuran tingkat kebisingan lingkungan
    This standard contains measurement method that is similar to Kepmen LH No.48 year 1996 which is to measure noise samples for 10 minutes across 24 hours period. Noise levels then can be calculated based on its time slice which are Ls (daytime noise), Lm (nighttime noise), and Lsm (day-night noise, with 5 dB penalty for nighttime).
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What you need to know about Room Acoustics

In the Southeast Asia region especially, acoustic properties of residential buildings are often neglected by designers, developers, contractors, and even home buyers. Noises from both internal and external environments affects occupants’ daily lives, causing nuisance which can strongly deteriorate one’s living quality as a long-term effect. In this article, we will investigate building/room acoustics, and the actions that can be undertaken to improve the acoustical environment inside a building.

Room acoustics

In general, the acoustics of rooms can be divided into two groups: low frequency and high frequency. Sound in rooms can be highly affected by the reflective properties of the surfaces in the room. This is because multiple reflections may occur if the room surfaces are highly reflective, which then leads to a reverberant field in addition to the direct field from the source especially at higher frequency range. Therefore, at any point in the room, the overall sound pressure level is influenced by the energy contained in both the direct and reverberant fields (Crocker, 2007).

Sound transmissions in buildings

Sound can be transmitted within a building by transmitting through air in the spaces bounded by walls or roofs/ceilings, known as airborne transmission. Another way would be through structural transmission through the structural assemblies of the building, or impacts.

Airborne sound originates from a source that radiates sound waves into the air, which would then impinge on the building surfaces. A good example of airborne sound will be speech, or music from a television or loudspeaker. On the other hand, impact sound is being generated when an object strikes the surface of a building. The commonly heard impact sounds that we can hear in buildings are footsteps, furniture-dragging sounds, cleaning, and other equipment that is used directly on the floor surfaces. To overcome these noises, good sound isolation should be considered for all the possible paths for sound and the junctions between walls and floors, not just at the direct path through common wall or floor.

Sound insulation – airborne and impact

It is imperative to consider the control of airborne and impact sound transmission through the building elements like walls, ceilings, or floors, as stated above. In this case, sound insulation methods will be crucial. Different methods can be implemented for airborne, impact and flanking sounds (Crocker, 2007).

For airborne sound, insulation can be applied at any building element. This is because when sound hits on a surface, a very small fraction of the incident energy will be radiated from the other side. The sound transmission loss (TL), which is the ratio of the incident sound energy relative to the transmitted sound energy is typically measured. TL can be expressed in decibels (dB), and it is sometimes known as sound reduction index (R) in European and ISO standards. The elements to be used in buildings for sound insulation are measured in accordance with standards, where the commonly seen method would be the two-room method. A test specimen would be mounted between a reverberant source room, and a receiver room such that the only significant path for sound to transmit through is the specimen, and other possible transmission paths would be suppressed. As such, it will be useful to determine the TL of the building elements/materials so that one can estimate the airborne sound insulation performance inside the building space.

As for impact sound which typically radiates from a floor into rooms below or horizontally, insulation can be done via floor coverings or floor slabs. This is because the applications of these items can reduce the impact sound pressure levels that travels into the receiver room. The typical methods of insulation are adding soft floor coverings on concrete slab, increasing the thickness of concrete floors, or implementing floating floors.

Single number ratings

To know the acoustic information of an insulation element, the standard method would be to refer to the single number ratings of that element. These ratings would be assigned to building materials based on their sound transmission spectra by the means of reference curves or weighted summation procedures.

The most used single-number rating for airborne sound insulation is the Sound Transmission Class (STC), which is in accordance with the American Society for Testing and Materials (ASTM) E413. There is another equivalent number called the Weighted Sound Reduction Index (Rw), which is based on the International Organization for Standardization (ISO) standard ISO 717.

The figure above shows an example of STC contour fitted to a concrete slab’s data. The differences between data points below the contour line and the value of contour are called the “deficiencies”. According to ASTM E413, the sum of deficiency should not be greater than 32 dB, and each individual deficiency should not exceed 8 dB (also known as the 8-dB rule). The reference contour for ASTM covers the frequency range from 125 Hz to 4000 Hz. The Rw contour from the ISO 717 has the same shape, except that it covers a broader frequency range of 100 Hz to 3150 Hz. Also, there is no 8-dB rule in ISO 717. Comparing both standards, the numbers from both ratings are usually close. However, the weighted summation method developed in ISO 717 accounts for the higher importance of low frequencies in traffic noise and modern music systems. As such, this method allows corrections/spectrum adaptation terms to be produced that can be used in conjunction with the Rw rating.

As for impact sound insulation, the sound pressure levels are often collected using a standard tapping machine and normalised, which will then be used with a reference curve to calculate its rating, typically the Impact Insulation Class (IIC), or the weighted index Ln,w. In fact, these ratings are commonly used in building codes. Again, the rating curves are identical in each standard, but there are some differences among them still. For instance, the ASTM IIC method does not allow any unfavourable deviation to exceed 8 dB. An increasing IIC rating would indicate that the impact sound insulation improves. Conversely, the Ln,w rating would decrease as the impact sound insulation gets better. We can take the relationship between both ratings as follow (assuming that the 8-dB rule is not invoked):

However, there is debate regarding the usefulness of ISO tapping machine data obtained on different types of floors. Therefore, the latest version of ISO 717-2 proposed the use of C1, a spectrum adaptation term to consider low-frequency noise that is normally generated below a lightweight joist floor.  is the unweighted sum of energy in the one-third octave bands (50 or 100 Hz – 2500 Hz) minus 15 dB. According to the standard, this rating is expected to have a better correlation with the subjective evaluation of noise coming below floors, especially for low frequency ones.

The single rating numbers mentioned above are all useful when it comes to determining the level of acoustic insulation a material can provide. With the explanation above about room acoustics and the insulation measures that can be implemented, it will give a better idea on how one should tackle and handle the room acoustics in a building.

References

Crocker, M. J. (2007). Chapter 103: Room Acoustics. In C. H. Hansen, & M. J. Crocker (Ed.), Handbook of Noise and Vibration Control (pp. 1240-1246). Adelaide, South Australia, Australia: John Wiley & Sons, Inc. doi:ISBN 978-0-471-39599-7

Crocker, M. J. (2007). Chapter 105: Sound Insulation—Airborne and Impact. In A. C. Warnock, & M. J. Crocker (Ed.), Handbook of Noise and Vibration Control (pp. 1257-1266). Ottawa, Ontario, Canada: John Wiley & Sons, Inc. doi:ISBN 978-0-471-39599-7

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Noise Barriers

Noise barriers are designed to resist the sound waves in the propagation path from source to receiver. In general, the closer the barrier is to the source the more effective it becomes. For simple plane barriers the height and length are the most important factors determining the degree of screening achieved and simple design rules have been developed to determine the reduction in overall noise levels.  These are based on the path difference between the direct path from source to receiver through the barrier and the shortest path passing over the top of the barrier. The greater this path difference the greater the screening. The shadow zone of the barrier is the region where the receiver cannot see the source and here the greatest reductions in noise levels are recorded. Some sound will always be diffracted over the top and around the edges of the barrier into the shadow zone so it is not possible to eliminate all noise from the source. However, typical barriers of a few metres high can achieve a worthwhile noise reduction of the order of 10 dB(A). This corresponds to halving the subjective loudness of the sound.

 

Figure (a)

Figure (b)

For more complex barriers simple methods are not appropriate and numerical methods such as the Boundary Element Method (BEM) have been used to produce accurate solutions.

Many different types of barrier have been installed using a wide variety of materials including wood, steel, aluminium, concrete and acrylic sheeting. Some of these designs have absorptive facings on the traffic side which reduce reflected sound. Barriers over 8 m in height have been used for some applications and novel capped barriers and angled barriers have been tested.

Barriers that may offer improved performance over simple plane barriers can be grouped under the following broad headings.

The above fig (a) shows the Main pathway of the sound propagation from the source to the barrier’s edge for sound walls with or without source-side absorption. Fig (b) shows Absorption material construction.

If smaller vehicles passing by the barrier, the reflection off the vehicle it does not play much of a role. Multiple reflections can only occur if noise barriers are built along both sides of the highway or train tracks.

In the case of large noise emitters, the implementation of source-side absorbent noise barriers can prevent the so-called zigzag effect

  1. Absorptive barriers—that is, barriers incorporating elements on the traffic face that absorb a significant proportion of incident sound and hence reduce reflected sound which could contribute to overall noise levels in the vicinity.
  2. Angled barriers—that is, barriers that are tilted away or have contoured surfaces angled to disperse the noise, the aim being to prevent significant sound reflections into the area where screening is required.

 

ABSORPTIVE BARRIERS

Where a plane vertical barrier is erected on one side of the road then sound reflections to the opposite side take place as illustrated in fig 1(a). In addition, reflections between vehicles and the barrier may lead to loss of screening performance as shown in fig (b). Where plane vertical barriers exist on both sides of the road, as shown in fig(c), they are normally parallel to each other and, in this situation, sound is reflected back and forth between the barriers again leading to a loss in performance. Absorbing panels located on the sides of the barriers facing the traffic can reduce this reflected contribution by absorbing the sound energy from the incident wave.

ANGLED BARRIERS

An alternative to using sound absorptive barriers is to angle the barrier or parts of the barrier away from the road such that the reflected wave from the traffic face of the barrier is deflected upwards, so reducing the contribution to noise at receptor positions relatively close to the ground. The performance of such barriers has been measured at full scale at TRL’s unique Noise Barrier Test Facility (NBTF).  The noise source used consisted of an 800 W speaker that can be positioned in front of the test barrier on a specially laid strip of hot rolled asphalt, thereby representing the traffic source on motorways and all-purpose dual carriageway roads. Microphones can be positioned to measure the noise level in the shadow zone of the test barrier at any point on a wide flat grassland area free of reflecting objects. To measure the acoustic performance of the barrier, recorded noise in a broad frequency range is broadcast and noise levels are measured at standard locations behind the barrier. Corrections can be made for variations in speaker output and wind speed and direction. In this way the screening performance of the barriers for a typical traffic noise source can be evaluated.

The above fig shows angled noise barrier.

Source : Various books and research journal

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SCOPE OF ARCHITECTURAL ACOUSTIC CONSULTANT’S WORK

What should an architectural acoustic consulting firm do? This question is very commonly asked when an acoustician is asked to submit a work proposal for a project. In this article, we will describe the scope of work of an acoustic consultant with reference to the type of mixed-use high-end building project. Because in this type of project an architectural acoustic consultant is required to be able to describe all the scope of work in one project with high complexity.

Details of the scope of work of acoustic consultants in mixed-use high-end building projects are as follows:

1. Criteria Formulation
At the beginning of the project, the acoustic consultant must recommend design criteria/targets for various rooms and areas within the building such as retail, apartment units both for bedrooms and living rooms, and commercial areas such as meeting rooms, multifunction rooms, spas, fitness, restaurants. , club lounges, etc. These criteria are determined based on studies and summaries of the applicable standards in the country, international standards, client recommendations, and the building operator concerned.

2. Schematic
With so many rooms that fall into the scope of work of an acoustic consultant with this type of project, it is highly recommended that an acoustician provide schematic designs for several important rooms for the attention of other consultants in the early stages of the project. Examples are MEP rooms, building structure connections, placement of HVAC equipment above the ceiling, and draft wall partition configurations.

3. Noise Review from the Environment Around the Building
The acoustic consultant must review potential sources of noise from aircraft, train stations, transportation on highways, outdoor MEP equipment, and all things around the building that have the potential to interfere with audial comfort to the interior of the building to ensure the targeted acoustic criteria are achieved. At this stage the acoustician must be able to convey the results of modeling and simulations for several points around the building in the form of drawings that can be understood by clients and other consultants. At this stage, a building fa konfigurasiade configuration can be recommended that takes into account the noise from the area around the building.

4. Noise HVAC (duct-borne)
Discussion and review of noise from all HVAC be it from air handling unit (AHU), axial and centrifugal fans, fan coil unit (FCU), etc. The ducting system will be analyzed to determine the noise level in the critical room from the nearest diffuser ducting system outlet. From this analysis, the need for silencers, lagging or duct linings will be recommended in order to achieve the acoustic criteria that have been determined. The analysis will be carried out on all HVAC systems without exception, with the greatest attention being on residential areas, spas, hotels, etc.

5. Sound Propagation in Building Structures (Structure-Borne)
All matters relating to the propagation or vibration of sound via the building structure, whether it is due to human footsteps on the top floor or vibrations from the installation of MEP machines above the ceiling or floor. The acoustic consultant must be able to evaluate according to the natural frequency of the building structure and provide recommendations on floor slab elements to meet operator and client standards applied.

6. Machine Vibration Control
The acoustic consultant should conduct an in-depth discussion on the vibration isolator for the installed machines. This is done by taking into account the deflection of the floor slab and its relationship to the static and dynamic loads of the machine (eg chiller, pump, cooling tower, AHU, etc.). In addition, ensuring the insulator is efficient to withstand vibrations to the building structure.

7. Room Insulation
Discussion on the isolation of certain rooms by providing technical calculations both with the “indoor room” and “floating floor” methods so that sound and vibration do not propagate to all elements of the building, especially the room around the isolated area.

8. Acoustic Interior
Reviewing and calculating room acoustic parameters on interior design elements of commercial spaces such as ballrooms, meeting rooms, and other areas where the clarity of speech or music is crucial.

9. Detailed Drawing
The acoustic consultant must provide or recommend specifications for building skin elements such as faades, walls and floor slabs in CAD format on a cut or plan basis. This will make it easier for relevant consultants to apply these specifications in their construction drawings.

10. Noise Isolation Due to Impact
Collisions in the fitness area, whether it’s due to aerobic activity or lifting weights, are a special concern for acoustic consultants. In addition to different forms of acoustic treatment, the time span of these activities must also be included in detailed technical calculations, and of course measurable.

11. Review of Related Consultant Drawings
After all acoustic treatments have been adapted to construction drawings by the relevant consultant, the acoustician must review all these drawings to ensure that all treatments have been described correctly, before entering the tender phase.

12. Coordination with Selected Contractors
The acoustic consultant must allocate time to coordinate the design and answer questions from the selected contractor and sign all forms related to material approval if it is in accordance with the acoustic intentions.

13. Final assessment
Before handing over the project to the next party, the acoustic consultant must conduct a final assessment of the building elements designed by the consultant. Next, compare the measured value to the design target and pre-determined criteria.

by Ramadhan Akmal Putra 

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Asia Noise News Building Accoustics Building Acoustics Environment Home Industrial Noise and Vibration Product News Noise-th Uncategorized Vibration Virtual Data Room

Accelerometer mounting

One of the challenges in measuring vibration using accelerometer is how to mount the accelerometer on the surface of the object that is being measured. Choosing the proper mounting can affect both to the measurement results and practicality when we are conducting the measurement.

 

Accelerometer mounting affects the measurement results because it can shift the resonance frequency of the accelerometer. Accelerometers have a significant amplification factor at its resonance frequency. This implies that in conducting measurements using accelerometer, it is important to choose mounting techniques that does not shift the resonance frequency into our frequency of interest.

 

Generally, there are four ways to mount accelerometer which are:

  1. Stud mounting: this technique is done by bolting the accelerometer into the object. This option is often considered as the mounting technique that produces the best measurement result compared to other options. Stud mounting has a high resonance frequency that in most cases a lot higher than our frequency of interest. To increase the performance of stud mounting, coupling fluid such as oil, petroleum jelly or beeswax can be used.

The downside of this technique is that not all object has a possible location to be bolted at the surface. If this is the case, then we will need to modify the surface and might leave a hole on the object.

  1. Adhesive: there are few adhesives that are commonly used to mount accelerometers such as epoxy (usually chosen for permanent mounting), wax, glue, and double-sided tape. Use of adhesive has lower resonance frequency compared to stud mounting, but in majority of cases still high enough that it does not affect the measurement at the frequency of interest. Of course, this depends on the type of adhesive that is being used as well.

Usage of adhesive however, especially for temporary mounting, has its own problem which is it can leave stain on the surface of the object that we are measuring, as well as on the accelerometer itself.

Another option of mounting related with adhesive is to use adhesive mounting pad, which is a pad that can be mounted on the surface that we want to measure using adhesive, and then we can mount the accelerometer on the pad. This will allow us to move one accelerometer to few locations more easily. From practicality perspective, adhesive mounting pad has an advantage if we want to repeat the measurement. Also, by using adhesive mounting pad, we avoid direct contact of adhesive to the accelerometer so that it will not need cleaning.

  1. Magnet: For metal surfaces, one of the options that is easy and does not leave stain is by using magnetic mounting base on the accelerometer so that we can attach the accelerometer to metal. This is the reason magnetic base is one of the best options especially for short-term and temporary measurement on metal.

However, this mounting technique produces lower resonant frequency compared to the other two options that we have discussed above. If the frequency that we want to measure is high enough, say above 1 kHz, this mounting technique might influence the measurement results.

  1. Handheld: In some of the cases, the three options above are not possible to be chosen, and it leaves us with the last option which is holding the accelerometer by hand. In this kind of cases, a probe tip can be used so that we can put pressure by hand on the surface that we are measuring easier.

We will have to pay more attention to the frequency range that we are measuring if this mounting technique is used. Because this option will reduce our frequency range significantly, generally only in the range of 10 – 100 Hz. 

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