Thẻ: noise

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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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Noise caused by construction works at night in Netizen

A video she had filmed of the construction site shows the drone of the machinery could be heard reverberating along with the backup beeper of a truck at the site. This can go on up to 3 am as reported by the netizen.

Singapore — A member of the public has taken to Facebook after she realized that construction works were being carried out near her apartment even at night, causing a lot of noise in the area. 

She put up a post on the Facebook group “Complaint Singapore” to seek advice from other netizens who might have encountered a similar situation before.

In her post, a member of the public also included a video she had filmed of the construction site. In the video, the drone of the machinery could be heard reverberating along with the backup beeper of a truck at the site.

According to the caption of the post, this was not the first time that such an incident had occurred. The member of the public also mentions that the construction works had gone on until 3 AM on a previous occasion. As such, she asked other netizens for help on who to contact on the issue, since the sounds generated by the construction works can be quite loud and disruptive.

Other netizens shared their views on the matter and offered suggestions in the comments section. 

A few netizens chalked the nighttime construction down to urgency, saying that there might be an emergency that needs fixing quickly and promptly.

Some other netizens thought that carrying out construction work at night, would impede the flow of traffic less since there are fewer commuters during the night.

A few other netizens suggested that the poster bring the issue up to the relevant authorities such as the National Environment Agency (NEA), the Land Transport Authority (LTA), or the Singapore Police Force (SPF).

After contacting NEA, the poster replied that they were helpful in stopping the works at an earlier hour.

According to NEA, construction sites need to observe the noise level and exercise construction noise control with effect from 1 Oct 2007. 

Credits: www.theindependent.sg

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The power of trees can reduce noise.

The way most workers need to complete tasks have significantly changed the way companies use their spaces. Quiet spaces are needed for deep, focused work. Technology enabled meeting rooms and collaboration spaces are used for productive meetings. Ideally, an office is designed in such a way that it enables team members to do their best work.

Unfortunately, it can be difficult to make sure a design includes all these aspects. As a result, designers and architects still often have to leave space for cubicles and open office spaces, a big contributing factor to general noise levels.

Did you know? Planting trees in your home or office not only helps to cool the internal temperature, increase the oxygen in the air give a feeling of freshness, and help relax only. But plants can also HELP ABSORB NOISE!

One creative way to both combat office noise and bring biophilic elements to a design is to incorporate plants and greenery into a space. Studies have shown that both plants and living green walls are an effective way to absorb sound and noise pollution.

Beyond their sound absorbing qualities, plants and biophilic elements can help to improve a worker’s overall well-being. Access to natural elements like greenery, natural light, and organic textures have been found to both improve employee productivity and reduce absenteeism. Plants have been found to be a mood booster and a stress reliever for team members, which can in turn, help to improve an employer’s bottom line.

Do Plants Help to Absorb Sound?

There is quite a bit of research on the subject, but the short answer is yes. The flexible and porous nature of indoor house plants acts as natural sound reducers. There are three ways that house plants can reduce the sound in your home or office: deflection, absorption, and refraction.

Most people do not understand the sound absorption benefits of houseplants. However, they really do help with absorption sound.

How Plants Reduce Indoor Noise Levels?

As mentioned above, plants reduce noise levels through three different methods: deflection, absorption, and refraction.

  • Deflection – Sound waves tend to bounce around off hard surfaces. That is where all that added noise comes from. Walls are rigid and will amplify sound, while plants are flexible and help to deaden the sound by breaking up the sound waves into other forms of energy.
  • Absorption – Plants are great at absorbing sound because of the leaves, branches, and wood. Wood is a great sound absorber. Have you ever walked through a forest and been amazed at the silence? That is because the trees are absorption all the ambient noise.
  • Refraction – Refraction is taking away the echoes of the sound bouncing off the hard surfaces. Plants will help to refract this noise and eliminate the echoes which are responsible for much of the added noise in your home or office.

The indoor plants that work best at absorbing sound such as:

  • Ferns: have a lot of surface space to help reduce sound. Their wide leaves spread out and cover quite a bit of area.
  • Baby’s Tears: Baby’s Tears are a dense plant that looks almost like moss. The plant has a way of draping itself over the pot and makes a great sound reducer when elevated off the ground.
  • The Peace Lily: The Peace Lily can absorb some of the sounds with their leaves and do a great job of bouncing the sound to the other plants and is a great sound absorbing plant you can put in your home. Their true noise absorbing properties are in their thick, broad leaves.
  • The Rubber Plant: The beauty of this plant is just how big it can get. Rubber plants cover a large surface area which only serves to enhance their sound absorbing properties.
  • Fiddle Leaf Fig: The fiddle leaf fig is another plant with broad, thick leaves. They can grow tall, and the cupped shape to the leaves make for an effective sound absorber.

Reference :

พลังจากต้นไม้ ลดมลพิษทางเสียง

https://bettersoundproofing.com/best-sound-absorbing-indoor-plants/

The Top Sound Absorbing Plants For The Workplace

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Industrial Noise Control Measure

In industrial places that are normally full of machineries or mechanical systems, noise is definitely inevitable, and in fact, very loud. This can sometimes be harmful to the workers hence causing occupational health and safety hazard. Therefore, in this article, we will look into noise control measures that can be used to overcome industrial noise in workplace.

Noise sources

Let’s begin with a recap on how noise is being produced:

Sound in general, is produced by vibration, or sometimes due to aerodynamic systems. Vibration-induced noises can be caused by multiple reasons, for example:

  • Mechanical shocks and friction between machinery parts like hammering, rotating gears, bearings, cutting tools etc.
  • Moving parts that are off-balanced
  • Vibration of large and heavy structures

As for aerodynamic noises, they are caused by air or fluid flows through pipes, fans, or pressure drops in air distribution systems as well. Typical examples of aerodynamic noise sources are:

  • Steam released through exhaust valves
  • Fans
  • Combustion motors
  • Aircraft jets
  • Turbulent fluid flow through pipes

Steps to control noise in workplace

To properly control the noise in the workplace, these steps should be carried out:

  1. Identify the sound sources (i.e., vibrating sources or aerodynamic flow)
  2. Identify the noise path from source to worker
  3. Determine the sound level of each source
  4. Determine the relative contribution to the excessive noise of each source and proceed to rank the sources accordingly. The dominant source should always be prioritised and controlled first in order to obtain significant noise attenuation.
  5. Understand the acceptable exposure limits as written in the health and safety legislation and find out the necessary sound reduction.
  6. Find out solutions while taking the degree of sound attenuation, operation, productivity restrains and cost into consideration.

To reduce exposure to noise

In general, noise exposure can be reduced by the elimination of noise source if possible, otherwise substitution of source with a quieter one or the application of engineering modifications works too.

The most effective way to minimise the exposure of noise is to engineer it out at the very beginning: the design stage. It is suggested to always choose equipment features that can reduce noise level to an acceptable level. For new installations, again select a quiet equipment, and make sure to have a procurement policy that opts for using quiet equipment, and finally eliminate any design flaws that may lead to noise amplification.

Engineering modifications refer to changes that can affect the source, or the sound path. This is usually the preferred solution for noise control in already-established workplaces (those without noise protection measures during design stage). This is because engineering modifications are known to be more cost effective, especially to control the noise at the source than along the path.

Administrative controls and the use of personal protective equipment (PPE) are also effective as measures of noise control applicable on workers themselves. A combination of both may be taken into consideration when the noise exposure would not justify the implementation of engineering solutions that are more expensive. However, it is important to always note that administrative control and PPE may not be as effective as implementing engineering noise control during the starting stage or modifications of sound path. Therefore, they should be categorised as the last resort.

Engineering solutions to reduce noise

Different solutions can be applied for vibration-induced noise and aerodynamic-noise.

For vibration-induced noise, the key point is to reduce the amount of vibration at the source. The typical solutions include modification of the energy source such as lowering the rotating speed of fans, or reducing the impact force of hitting tools etc. Adding damping materials onto vibrating surfaces due to mechanical forces can help to reduce vibrational effects too, especially for thin structures. To prevent unwanted damage due to friction or impact, the damping material may be sandwiched between the surface of equipment and another material that is resistant to abrasion. This treatment is called the constraint layer treatment.

Other methods to reduce vibration-induced noise include minimising gaps in machine guards and cover them with acoustic-absorbent material, replacing metal parts with plastic parts whenever possible, and replacing motors with quieter ones.

On the other hand, to treat aerodynamic-induced noise, specialists recommended to implement engineering practices that are capable of reducing noise associated with unstable fluid flow, for example minimising fluid velocity, increasing pipe diameter or minimising turbulence by utilising large and low speed fans with curved blades.

Besides those mentioned above, there are also passive noise control measures that can be used. These include using enclosures and isolations by storing noisy equipment in enclosed spaces/rooms that have special acoustic features like isolation, louvres or sealings. Installations of acoustic barriers (sound-absorbing panels) in workplaces, or silencers inside ducts and exhausts works well in attenuating unwanted noise too.

General measures to keep in mind

Finally, here are some general methods that one can take to ensure that workplace noise is under controlled.

Regular maintenance should always be performed, where the focus should be on identifying and replacing any worn-off or loose parts, lubricating any moving parts, and make sure that the rotating equipment does not get off balance to avoid vibration-induced noise.

Noisy processes should be taken note about and be substituted with quieter ones. Sound reverberation in the room should be reduced. Reverberation is when sound produced in an enclosure hits reflective surfaces and reflects back into the room in addition to the original noise paths. In some cases, reverberated sounds may dominate the original sound. A good method to help in such conditions will be to add padding onto the reflective surfaces with sound absorbing materials so that noise level can be reduced. Another way will be to arrange the equipment in the room so that they are not too close to too many reflective structures.

Conclusion

In conclusion, always take measures to identify the sound sources in the industrial workplace and find out suitable ways to solve the noise issues to achieve noise limits in accordance with exposure limits set in the health and safety legislation published by the local authorities. It is utmost important to obey the noise exposure limits to ensure the hearing health of workers in the workplace.

Reference

https://www.ccohs.ca/oshanswers/phys_agents/noise_control.html

https://www.who.int/occupational_health/publications/noise10.pdf

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Hotel Room Acoustics – how noise affects a person’s stay in the hotel

Hotel Room Acoustics – how noise affects a person’s stay in the hotel

Hotels have been playing an important role during the current pandemic. In certain countries, the local governments have announced that it is compulsory for those entering the country from overseas to carry out hotel quarantine. Taking Malaysia as an example, travellers entering the country regardless from any country are required to undergo hotel quarantine for up to 10 days (as of January 2021), in which the local authorities will arrange the rooms for them unless the travellers opted for Premium Package which of course, costs higher than the standard ones. Travellers will have to take COVID tests in between to ensure that they are COVID-negative and isolating them in the hotels will make sure that there will not be the possibility of spreading the virus to the public since all travellers should be taken as potential risk carrier.

Hotel room comfort

Many may be wondering: How is the cleanliness of the room? Are the meals provided good? What about the Wi-Fi strength there?

But there is one thing that people sometimes forget about: Noise. From the study done by the J.D. Power North American Hotel Guest Satisfaction Survey, it has been consistently shown that complaints on noise issues are significantly under-reported, and hardly being resolved in the end (Simonsen, 2019). Imagine living in a confined space for more than 10 days, where you need to experience constant noise coming from your neighbours, or from outside the room like traffic or construction noise, how will you feel? Looking at some hotel review posts in the Malaysia Quarantine Support Group (MQSG) created to aid travellers coming into Malaysia, there seem to be numerous posts complaining about noise nuisance during their quarantine period. The typical problems faced by members include:

  1. Traffic noise – hotel is located next to busy road
  2. Construction noise in the day from nearby sites
  3. Loud neighbours – speaking loudly especially at sleeping hours

To be exact, these are the similar nuisance one would experience in residential houses.

For short term stays, these may not be the main concern, but it is a totally different case for a quarantine. Unreasonable amount of noise daily for long term, especially after a tired flight and transition at the airport, will lead to unwanted circumstances on a person’s health (physically and mentally).

Noise and Sleep Disturbance

For people who are extremely sensitive to noise, the first thing that can be observed will be that they cannot sleep or even rest well. This will result in sleep deficiency, which slowly drains off the energy to carry out daily tasks. According to Hume, many from the research field claimed that sleep disturbance caused by environmental noise has the most detrimental effect to health. Having an undisturbed night of sleep is even taken to be a fundamental rights and prerequisite to ensure continued health and well-being (Hume, 2010). Hume mentioned that noise pollution can be described as the “modern unseen plague” which may interfere with cognitive processes hence disturbing sleep quality.

To overcome the problem of noise affecting sleep quality, the World Health Organization (WHO – European Office) has brought in experts with relevant documents in recent years to establish the Night Noise Guidelines for Europe. The guidelines contain the latest reviews of noise disturbance and the potential risk to human health. Below are the four ranges of continuous external sound level at night, relating night noise and the populations’ health effects:

<30 dB – no substantial biological effects could normally be expected

30-40 dB – primary effects on sleep start to emerge and adverse effects in vulnerable groups

40-55 dB – sharp increase in adverse health effects while vulnerable groups become severely affected

>55dB – adverse health effects occur frequently with high percentage of the population highly annoyed

These guidelines help to understand the effect of noise on sleep, although a large extent of this topic still relies on fully understanding the fundamentals of the nature of sleep.

Acoustics Solutions for Hotels

As mentioned in the previous sections, the noise complaints for hotel rooms mainly cover traffic noise, noise from neighbours and construction noise. Since sound travels in wave forms, soundproofing will be one of the best concepts to act as a barrier that can effectively stop the sound waves from entering a room from outside.

Typically, there are four methods to achieve the soundproofing effect for hotel rooms (SoundGuard, 2019):

  • Absorption – adding sound insulating materials such as mineral wool or fiberglass for sound absorption, thus preventing sound from passing through
  • Damping – soundwaves often cause vibrations between air particles. Damping helps in reducing or eliminating the vibrational effects by acting as a barrier that does not vibrate
  • Decoupling – In layman terms, this also means separating the walls by adding an insulation layer between the two layers of drywall.
  • Mass – Utilizing thicker, heavier, or denser materials to block sound

While choosing the right material for insulation, it is important to take note on the Sound Transmission Class (STC) rating. The STC rating defines the effectiveness of materials in attenuating airborne sound. The lower the STC rating, the less sound that can be effectively blocked. Therefore, to achieve good insulation results, it is better to use a material with higher STC value.

When should you implement acoustical solutions?

Ideally, it is best to start from the very beginning, which is during the project planning stage (yes, before you even start building it!). Quoting a line said by Scott Rosenberg, the president of Jonathan Nehmer + Associates, and the principal with HVS Design, “You have to think about the inside walls like they’re on the outside” (Fox, 2018). This was said for atrium style hotels which are normally structured like giant echo chambers, where noise from the lobby may travel up to the penthouse suite due to the structure. In the planning stage, allocating which part of the hotel goes where is also crucial to make sure you keep sounds in the right places, and nowhere else. For example, it is important to locate the facilities like gyms, pub, or even spa strategically so that the noise from these places will not affect the guests staying in the hotel rooms. If you really must put them above/below rooms, make sure to use walls or ceilings that are properly insulated.
For existing hotels, another good time to improve the acoustics of the hotel will be during renovation periods. Since you took the step to upgrade your hotel looks and structure, why not consider soundproofing as well? It will definitely help to raise the customers’ satisfaction during their stay.
The areas that can be considered for hotel soundproofing during renovation include:
• Floors – adding soundproofing underlay
• Ceilings – using decoupling methods (dual-layered drywall)
• Doors – changing to solid-core heavy doors with seals
• Walls – adding insulation between walls / use soundproofing paint

 

How do you know if your hotel needs acoustical improvements?

Although some may only start treating the problem after getting significant complaints from customers, hotel owners should consider taking the initiative to find out the noise condition in the building. A good start will be to carry out noise measurement tests to monitor the condition in each room. Having noise data from the measurements will help you understand what the situation is, and how you should resolve them. This is where an acoustics consultant should step in.
It is suggested to consult the acoustics specialists to get the most suitable solution for your case, because not all solutions can be applicable for all conditions. Acoustics consultants can help you to analyse the condition by using methods like indoor noise mapping, material insulation calculations and even tiny suggestions like adding certain types of furniture to aid sound absorption in the room itself.


Effects of Acoustics Improvement to the Hotel

It is proven that by enhancing the acoustics of hotels, business can be improved too. For example, Premier Inn in the UK has pioneered the new design of “floating bedroom” in 2011 at its hotel in Leicester Square. This new design allowed the hotel to resolve the environmental noise and the noise coming up from the nightclub on the ground floor. Premier Inn had also changed their focus from cost to customers’ sleep quality, which enabled them to become one of the best-rated hotels in London (Simonsen, 2019). Thus, the hotels’ business and reputation will strongly improve by taking care of the noise aspects.
Now, back to the starting topic of this article. Hotels are no longer only used as the accommodations for vacations or business trips. Hotels play an important part during this pandemic, being the quarantine centres in many countries. Therefore, it is important to ensure the customers’ (or those under quarantine) comfort during their stay, voluntarily or not. Their reviews make a lot of difference, which will highly impact a hotel’s image to the public. Most importantly, good, soundproofed room means less noise, resulting in better living and sleep quality. Hence, hotel owners are urged to investigate the acoustics aspects of their property, for themselves, and for the customers.


References

Fox, J. T. (2018, July 17). Careful hotel design keeps noise in check. Retrieved February 4, 2021, from Hotel Management: https://www.hotelmanagement.net/design/careful-hotel-design-keeps-noise-check


Hume, K. (2010). Sleep disturbance due to noise: Current issues and future research. Noise Health, 12(47), 70-76. Retrieved February 2, 2021, from https://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2010;volume=12;issue=47;spage=70;epage=76;aulast=Hume


Simonsen, J. (2019, June 20). Why and how to reduce noise in hotel rooms. Retrieved February 3, 2021, from Rockwool: https://www.rockwool.com/group/advice-and-inspiration/blog/why-and-how-to-reduce-noise-in-hotel-rooms/


SoundGuard. (2019). Hotel Sound Reduction – How to Soundproof a Hotel Room. Retrieved February 3, 2021, from SoundGuard: https://soundguard.io/hotel-sound-reduction-soundproof-hotel-room/

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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.

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Asia Noise News

Coronavirus Lockdown Gives Animals A Rare Break from Noise Pollution

The COVID-19 lockdown could become an unprecedented natural experiment in noise pollution. Some of the world’s most vocal animals — birds and whales — might already be benefiting from a quieter environment.

While a drop in transportation during the coronavirus lockdowns has led to lower pollution levels across the world, the slowdown in traffic has also lowered another big polluter: noise.

According to the World Health Organization (WHO), noise pollution affects over 100 million people across Europe and, in Western Europe alone, road traffic accounts for premature deaths equivalent to the loss of roughly “1.6 million healthy years of life.” 

Take the disturbance to human health out of the equation, and noise remains a big source of pollution for the other inhabitants of the planet as well, namely, animals. 

But how much have animals in countries on lockdown really benefited from the drop in noise levels? Turns out, that’s a very difficult question to answer.

Birds will benefit the most

Birds — by far the most visible animals found in cities, and the most vocal — stand to be among the biggest beneficiaries of quieter streets and parks. 

The signals birds send each other through song is a means of survival. Without the ability to sing, hear and be heard, birds would have a difficult time finding a mate or defending their territory from predators.  

There are reports of seeing more birds during the lockdown. Ornithologists say this is due to increased awareness of people’s surroundings while at home

Human activity influences bird behavior, even prompting them to communicate at less ‘busy’ times of day

The swift rise of human-made noise — also known as anthropogenic noise — over the past century has made this harder for birds. 

Just like humans who have to speak up in a loud setting, birds, too, have to sing louder to communicate properly in today’s noisy world, according to ornithologist Henrik Brumm, who heads the research group for the communication and social behavior of birds at the Max Planck Institute for Ornithology near Munich.

“This happens really fast,” Brumm told DW. “We found out that it takes roughly 300 milliseconds, so less than 1 second, for birds to readjust when the level of noise rises. So, when their surroundings become louder, they sing louder, too.”

Are birds getting quieter? Maybe.

Birds are already known to sing more quietly in the early morning hours of the weekends, says Brumm. The reason: there’s less traffic to compete with. 

With Europe on lockdown, Germany for its part, has seen passenger air travel slashed by over 90%. Moreover, car traffic has dropped by more than 50% and trains are running at less 25% their usual rates.

A recent study from the Max Planck Institute also suggests that chronic traffic noise can have a negative effect on embryo mortality and growth in zebra finches. This, in turn, could mean that the current lockdowns coinciding with mating season could lead to not only more, but also healthier hatchlings. That is, as long as their parents choose a spot that’s still safe from humans after the lockdown ends.

Though it’s difficult to speculate without real-time data, Brumm says, it stands to reason that the current period of quiet could mean birds might be singing more softly than usual, which would already be a huge benefit.

At land or sea, noise is bad news for animals

Birds aren’t the only animals that stand to benefit from less noise. According to a recent study published in the journal Biology Letters, noise pollution affects any number of creatures ranging from frogs, to shrimp, to fish, mammals, mussels and snakes.

In fact, another habitat garnering more and more attention for noise pollution is the ocean. As bioacoustics expert Christopher Clark described it in with Yale’s environmental magazine, the din from oil and gas activity, for example, is filling entire ocean basins with “one big storm of noise.”

While research on noise pollution and marine life, just like with ornithology, is in its early stages, a landmark study conducted in the days after 9/11 found that less shipping traffic seemed to make whales calmer.

Examining the feces of right whales — a species of baleen whale that can reach 15 meters in length and weigh up to 70 tons — researchers found that fewer ships in the waters along the US-Canadian coast correlated with lower stress hormones.

The noise levels from shipping traffic, whose 20–200 Hz hum disturbs sea life despite being a low frequency, decreased by 6 decibels, with a significant reduction below 150Hz .

An unprecedented time for researchers

Just like ornithologists, marine life researchers have also found correlations between noise and interruptions in behaviors like foraging and mating. Whales, like birds, also “mask.” That is to say, they sing louder to be heard over noise disturbances, be they high or low frequency sounds.

“It’s really a huge footprint that these activities have in the ocean,” according to Nathan Merchant, an expert on noise and bioacoustics at the UK’s Centre for Environment, Fisheries and Aquaculture Science (CEFAS).

Source: https://www.dw.com/

And the sources of noise pollution — ranging from shipping, to wind farms, to the sequence of powerful blasts from seismic air gun tests used to locate oil and gas deposits in the ocean deep — are even harder to escape in the ocean than on land.

“It has a lot to do with how sound travels under water. Sound can travel much further and much faster than in air,” Merchant told DW.

Instruments off the coast of North America, for example, can detect seismic air gun testing as far away as the Brazilian coast.

With many cruises suspended, oil freighter traffic impacted by an oil price crash and rig activity being run by skeleton crews to curb the spread of COVID-19, marine biologists could potentially find a treasure trove of data once they’re allowed to go back into the field. 

“We have underwater noise recorders at sea as we speak, but they aren’t cabled to land. So, we’ll find out when get out on a ship in several months’ time and get the data back,” Merchant said. 

The more interesting question by that point might be how marine life responds to a sudden reintroduction of the human cacophony after an unexpected period of rest.

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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!

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Building Accoustics

Researchers Develop ‘Acoustic Metamaterial’

Boston University researchers, Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph.D. student in the Department of Mechanical Engineering, released a paper in Physical Review B demonstrating it’s possible to silence noise using an open, ring-like structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.

They calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves, preventing sound—but not air—from being radiated through the open structure. The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they say.

As a test case, they decided to create a structure that could silence sound from a loudspeaker. Based on their calculations, they modeled the physical dimensions that would most effectively silence noises. Bringing those models to life, they used 3-D printing to materialize an open, noise-canceling structure made of plastic.

Trying it out in the lab, the researchers sealed the loudspeaker into one end of a PVC pipe. On the other end, the tailor-made acoustic metamaterial was fastened into the opening. With the hit of the play button, the experimental loudspeaker set-up came oh-so-quietly to life in the lab. Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away.

The metamaterial, ringing around the internal perimeter of the pipe’s mouth, worked like a mute button incarnate until the moment when Ghaffarivardavagh reached down and pulled it free. The lab suddenly echoed with the screeching of the loudspeaker’s tune.

How acoustic metamaterial works – Geonoise Asia
How acoustic metamaterial works – Geonoise Asia

Now that their prototype has proved so effective, the researchers have some big ideas about how their acoustic-silencing metamaterial could go to work making the real world quieter.

Closer to home—or the office—fans and HVAC systems could benefit from acoustic metamaterials that render them silent yet still enable hot or cold air to be circulated unencumbered throughout a building.

Ghaffarivardavagh and Zhang also point to the unsightliness of the sound barriers used today to reduce noise pollution from traffic and see room for an aesthetic upgrade. “Our structure is super lightweight, open, and beautiful. Each piece could be used as a tile or brick to scale up and build a sound-canceling, permeable wall,” they say.

The shape of acoustic-silencing metamaterials, based on their method, is also completely customizable, Ghaffarivardavagh says. The outer part doesn’t need to be a round ring shape in order to function.

“We can design the outer shape as a cube or hexagon, anything really,” he says. “When we want to create a wall, we will go to a hexagonal shape” that can fit together like an open-air honeycomb structure.

Such walls could help contain many types of noises. Even those from the intense vibrations of an MRI machine, Zhang says.

According to Stephan Anderson, a professor of radiology at BU School of Medicine and a coauthor of the study, the acoustic metamaterial could potentially be scaled “to fit inside the central bore of an MRI machine,” shielding patients from the sound during the imaging process.

Zhang says the possibilities are endless, since the noise mitigation method can be customized to suit nearly any environment: “The idea is that we can now mathematically design an object that can block the sounds of anything”.

Source:

https://phys.org/news/2019-03-acoustic-metamaterial-cancels.html

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Asia Noise News Building Accoustics

Are You Stressed at Work?

Are you stressed at work?

How many times did you need to cover your ears at work? You might be stressed because you are working in a noisy environment even without realizing it.

A noisy environment is one of the primary stress triggers for the employee and it will lead to a reduction in productivity. It is dangerous for your health but it could also impact your bonus at the end of the year? Let us remind you how noisy your working environment is by mentioning some sources:

  • Copy machines
  • Obnoxious ringtone
  • Computers
  • Air Conditioning
  • Noises from outside the office buildings (Trucks, Airplanes, Highway noise, nearby constructions)
  • Laughing/Talking
  • Gossip about boss
  • Gossip about co-worker who is not invited into WhatsApp Group

Those are common noise sources that might be contributing to the noise around you. We must remember that the distinction between noise and sound is very subjective. It can be particular to each person and even depend the situation.

Noise and sound can both be dangerous for your health and can be easily measured to quantify. The graphic below shows some noise levels. Fifty decibel would be great for a working environment, exposure for long time to noise levels above 80 decibel will permanently damage your hearing.

 

How Loud is Too Loud? – GeoNoise Asia

 

After reading the graphic, please take a moment to think about how many decibels your ears have to endure daily? Let’s say that you’re working in a general business noisy office. The noise levels can be reaching up to 90 decibels because of the cumulation of various noises such as laughter, yelling, ringtones, etc. The World Health Organization (WHO) claims that exposure to noise causes stress, anxiety, depression, high blood pressure, and heart disease. Furthermore, loud sounds will damage sensitive structures of the inner ear and cause noise-induced hearing loss (NIHL).

The damage because of the noise exposure is gradual; you might not notice the signs or you ignore them until they become more apparent. Here are the symptoms of the Noise-induced Hearing Loss:

  • Sounds have become distorted or muffled
  • You can hear people, but you can’t quite understand what they’re saying
  • You can’t hear or understand speech from 3 feet away or farther
  • You must turn the volume up more than others do in order to hear it as well as they can

All checked?

Please call professional help immediately! If it is not, congratulations, you still have a good hearing. But it doesn’t guarantee you that you will be free from NIHL.

Here are the tips on how to stay sane in a noisy working environment and prevent the NIHL at the same time:

•   Bring earplugs to your work!

You only need to spend a few thousand rupiahs for this. Wearing earplugs can help you to reduce the noise by 18 – 34 decibels. It depends on the models/brand. By blocking/reducing that amount of noise, you’re still able to hear the sound around you.

•   You might want to try the Noise Cancelling Headphones

It is made for keeping the noise away from your ears. If you use this in the office, it not only will help you block the annoying noise but also will make your music sounds way better than any other headphones in the same situation. The price ranges between a hundred thousand rupiah – millions of rupiah. It is an excellent investment, though!

•   Take a break!

When the noise around you is too much to handle, give your ears a break! It gives your eara time to recover from the stressful sound and this action also a preventive way to the damage of your ears. None of them seems to be working for you? Please contact the acoustical consulting service. They will help you to find the best solutions to your problems.

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