Tag: Acoustic Environment

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Asia Noise News Building Accoustics Environment Industrial

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

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

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

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

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

Where r is the distance from source to receiver

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

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

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

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

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

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

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

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

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

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

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Asia Noise News

Dogs Can Experience Hearing Loss

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Written by:

Pitupong Sarapho (Pond)
Acoustical Engineer

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

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

Categories
Asia Noise News Building Accoustics

Railway Noise

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

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

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

Exploring Jakartan Public Transportation Through The Sound

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

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

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

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

Written by:

Hizkia Natanael

Acoustical Design Engineer

Geonoise Indonesia

hizkia@geonoise.asia

Reference:

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

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

Categories
Asia Noise News

Acoustics Glossary

Get a better understanding of acoustics with our glossary of terms. Let Geonoise Instruments help you solve your noise problems today!

Geonoise Instruments Acoustics GlossaryDownload

Arranged by:

Adetia Alfadenata

Acoustic Engineer

Geonoise Indonesia

support.id@geonoise.asia

Categories
Asia Noise News

A Review of Acoustics in the Hospitality Industry: A Subjective and Objective Analysis

Many bars, cafés, and restaurants have been built in Asia, that is one of the indications that the hospitality industry is moving forward. Our need for entertainment, refreshing our mood, and communication with friends, family members, or business clients are reasons why we need the hospitality Industry such as; bars, cafés, and restaurants as a place for us to do that kind of activities. Comfortableness becomes a top priority to determine if a bar, café, or restaurant is a pleasant place to be or not. One of the criteria is comfortableness in acoustics aspect, how easy the customers can have a conversation, a relaxed ambience and quietness. In Asia, especially in developing countries, acoustic comfort in bars, cafes or restaurants is not yet a major concern, even though the effect will be huge for their visitors’ comfort. One example of the impact of bad acoustic design on a cafe or restaurant is the difficulty of communicating, even though one of the things that visitors want to do is chat with family, friends or work partners. This situation will give a bad impression of the café or restaurant and reduce the number of visitors to the café or restaurant.

In this article, the author will discuss the research conducted by Lauren H. Christie and J. R. H. Bell Booth – Victoria University of Wellington. This study is titled “Acoustics in the Hospitality Industry: A Subjective and Objective Analysis” this research examining several Bars, Cafes, and Restaurants around Wellington CBD related to acoustic comfort based on objective and subjective parameters which are then compared to AS / NZA 2107:2000.

The results of the research at the cafés, bars and restaurants in Wellington CBD found that the average noise level that occurred was 80 dBA and could even reach as high as 110 dBA. If it is compared with the level of sensitivity of human hearing to speech that only ranges from 48 dBA to 72 dBA [AS / NZA 2107: 2000] this very much exceeds the limit. The NC (Noise Criteria) suggested in this study are:

  • Bar : 45 – 50 dBA
  • Café : 45 – 50 dBA
  • Restaurant : 35 – 50 dBA

As reviewed earlier, research conducted by Lauren H. Christie and J. R. H. Bell Booth takes 2 parameters, they are subjective and objective parameters. Subjective consists of a Survey Questionnaire that is spread to visitors about the information conveyed, the ability to listen, the dominant difficulties that occur, and the desired ideal conditions. This is called subjective because it is qualitative and is adjusted to personal tendencies. The second parameter is Objective, consisting of measured parameters such as BN (Background Noise), Leq, RT (Reverberation Time), STI (Normal, Rise, Loud, Shout).

BN is measured by measuring the level of sound pressure in conditions without visitors, the use is as an acoustic base value without additional noise. Leq is the average noise over a period of time, this is done as sample information on the noise value of the place. RT or Reverberation Time is the time required for the sound to decay as much as 60 dB, this parameter is used as a base for evaluating the comfort of the conversation or music in a room, RT that is too high will make someone difficult to communicate because the sound will be reflected and reduce the clarity of the conversation. STI or Speech Transmission Index is a parameter to assess the level of comfort in terms of listening to speech or conversation, the value ranges from 0 to 1 with a value of 1 is perfect or very clear STI.

The age range of visitors looks similar if evaluated based on the survey, most visitors in a bar are under 25 years old, while in the cafés and restaurants most visitors are in the range of 25 – 35 years old. Based on the survey results, the need for acoustic quality related to the highest conversations is in restaurants, followed by cafés and bars. This is very clear because the restaurant visitors have a lot of verbal interaction or direct communication when eating. At the café, there tends to be less communication and more listening to the ambiance and relaxing music with less communication if we compare it with a restaurant. The last ranked is the bar, visitors will only listen to music to arouse their mood and rarely communicate. The highest source of noise comes from other visitors’ communications, which is followed by the sound of music and kitchen equipment.

Acoustic comfort based on survey results or subjective parameters are as follows:

Restaurant

  • Restaurants are expected to have a low Background Noise and a good STI, but the actual situation in most of the restaurants researched is far from that.
  • Privacy is a very important variable in a restaurant.
  • The clarity in terms of speech is low.
  • Visitors in the restaurants are very difficult to be heard/understood when they are talking.

Bars

  • Bar customers said that a bar is more acceptable to noise than a cafe or restaurant.
  • Even though it is difficult to communicate, the bar can be accepted by visitors.
  • Bar customers need more effort to communicate.
  • The type of people who visit the bar are people who are accustomed to noisy environments.

Café

  • People who often visit a café find it easy to communicate at the café.
  • Clarity of speech is seen as a more important factor than the visitor’s environment.
  • Café is also rated as the most unacceptable environment from this acoustic-related survey.

Based on objective parameters, the results are: BN (Background Noise is in the range of 34 dBA (Leq) to 81 dBA (Leq), where 60% of the data is worth more than 50 dBA (Maximum level in AS / NZA 2107: 2000). After measuring with visitors inside, the level of the noise reaches 25dB beyond the maximum visited level, but when compared to the OSH recommendation safety limit, 85 dBA (Leq), the value is still below the threshold (the highest level of measurement is 81 dBA).

For the RT value, both the bars, cafés and restaurants are within the standard of <1.0 S. STI rating is found to be very diverse, but from the use of the 4 types of sound that are normal, raised, loud, and shout the same pattern is obtained, the higher the sound level, the better STI. From this research, we know that there are differences in preferences of acoustic comfort factors in bars, cafes, and restaurants. The difference in preferences is due to differences in the main functions of each hospitality industry. At the restaurant, visitors expect to be able to communicate well in one scope of the table and maintained privacy from the scope of another table. At the café, the need for tranquility is the main thing and the need for communication is not as high as the restaurant. At the bar, the main needs of visitors are listening to music and not too concerned about communication difficulties.

So, has your hospitality industry considered acoustic comfort? It’s a very important aspect to keep visitors coming back to your venue!

Written by:

Betabayu Santika

Acoustic Design Engineer

Geonoise Indonesia

Beta@geonoise.asia

Source:

AS/NZS 2107 (2000). Acoustics – Recommended design sound levels and reverberation times for building

interiors. Australian/New Zealand Standards: Sydney/Wellington.

Bell-Booth, J. R.H. (2004). Methodology Research.

Christie, L. H. (2004). Acoustical Comfort: Research Design into Measuring Restaurants and

Bars Acoustic Environments.

Christie, L. H. & Bell-Booth, J. R.H. – Acoustics in the Hospitality Industry: A Subjective and Objective Analysis

Thailand