Category: Building Accoustics

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Building Accoustics

ISO 3382-1 Committee Draft Released: Why This Revision Matters for Room Acoustics

ISO 3382-1 Committee Draft Released
ISO 3382-1 Committee Draft Released

Introduction

The committee draft of ISO 3382-1 has just been released. This international standard defines how we measure reverberation time (RT) and related room acoustic parameters in performance spaces such as concert halls and theatres.

While the details may seem subtle, a revision here carries weight: it impacts how acoustic consultants, architects, contractors, and venue owners design, specify, commission, and verify music and speech venues worldwide.

What is ISO 3382-1?

ISO 3382-1, titled “Acoustics — Measurement of room acoustic parameters — Part 1: Performance spaces”, provides standardized methods for measuring:

  • Reverberation Time (RT)
  • Speech Clarity (C50)
  • Music Clarity (C80)
  • Other room-acoustic parameters critical for performance spaces

This standard ensures consistency in design evaluation, acoustic measurements, and project acceptance criteria across the globe.

Why Do These Revisions Matter?

Even minor changes in definitions, procedures, or tolerances can ripple across multiple phases of a project:

  • Design briefs: Consultants may need to adjust specifications for compliance.
  • Commissioning & acceptance testing: Measurement methods may be more stringent or redefined.
  • Verification: Test results must align with updated tolerances.

In short, these updates could affect everything from the initial design intent to the final handover of performance spaces.

Who Should Pay Attention?

  • Architects & Acoustic Engineers → Must update design methods to remain compliant.
  • Contractors & System Integrators → Measurement and acceptance workflows may shift.
  • Venue Owners & Operators → Compliance impacts usability, reputation, and performance quality.

Looking Ahead

The upcoming revision of ISO 3382-1 may tighten requirements on how we specify and verify room parameters, ensuring more reliable and standardized results across the industry.

Geonoise Asia will continue to monitor these changes and provide independent consulting to help clients stay aligned with the latest standards in room acoustics and building acoustics.

Contact Geonoise Asia
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Building Accoustics

5 Common Acoustic Design Mistakes in Architecture — And How to Avoid Them

Common Acoustic Design Mistakes in Architecture — And How to Avoid Them
Common Acoustic Design Mistakes in Architecture — And How to Avoid Them

In today’s evolving Thai architecture scene, client expectations go beyond beauty and functionality. Acoustic comfort and noise control are fast becoming essential standards for high-quality buildings — whether it’s a luxury condo in Bangkok, a resort in Phuket, or a new hospital in Chiang Mai.

However, we still see beautifully designed buildings suffering from poor sound environments because acoustic planning was treated as a secondary issue. At Geonoise Thailand, we’ve seen how proactive noise and vibration planning from the start of a project can prevent problems before they arise. Here are five common mistakes Thai architects make when acoustics are not integrated early — and how to avoid them.

1. Choosing the Wrong Materials for Sound Control

Issue: Materials are often selected for thermal performance or aesthetics, but not for sound. For example, thin gypsum walls or unsealed glass panels may look modern but allow noise to pass through easily.

Solution: Understand the sound insulation ratings of materials, such as STC or RW values, and consult an acoustic expert to select the right components for the noise levels expected.

2. Ignoring Building Services Noise

Issue: Mechanical noise from air conditioning units, water pumps, elevators, or generators can severely disturb spaces that need quiet, like bedrooms, classrooms, or consultation rooms.

Solution: Plan M&E systems with acoustics in mind — use vibration isolation, strategic placement, and proper sound insulation from the design stage.

3. Poor Room Layout Without Acoustic Zoning

Issue: Quiet spaces (like meeting rooms or bedrooms) are sometimes located next to noisy zones (kitchens, trash rooms, lift lobbies) without proper separation.

Solution: Use acoustic zoning — place noisy and quiet areas strategically, with buffer zones or sound-rated partitions in between.

4. Underestimating Low-Frequency Noise

Issue: Bass-heavy sounds from music, rooftop machinery, or subwoofers can penetrate walls and travel far, disrupting even well-insulated rooms.

Solution: Use noise modeling tools and select high-mass materials or vibration-damping designs to control low-frequency sound.

5. Bringing in an Acoustic Expert Too Late

Issue: Consultants are often called in after construction or when residents complain — fixing issues at this stage is usually expensive and limited.

Solution: Engage an acoustic consultant during the conceptual or schematic design phase. Early involvement helps resolve potential problems while saving time and cost.

Conclusion

Acoustic comfort is no longer optional — it’s a new benchmark for quality buildings. If you prioritize sound early in your design process, you’ll add real value to your architecture and strengthen your professional reputation.

At Geonoise Thailand, we support architects with precision tools, ISO17025-compliant services, and real-world experience. We ensure every decibel is managed effectively.

Want expert support from the start of your project? 

 

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Building Accoustics Environment Home Noise Technology

Use technology to mitigate disruptive noise

Use technology to mitigate disruptive noise
Use technology to mitigate disruptive noise

Singapore, a city-state renowned for its densely populated residential high-rises, consistently struggles with noise pollution.

Noise complaints increased dramatically during the Covid-19 pandemic; in 2021, the Housing Board received as many as 3,200 complaints per month, which was a marked increase over pre-pandemic levels.

The government has urged locals to address noise complaints with their neighbors directly or with the assistance of community leaders. If that doesn’t work, there is always mediation and, as a last resort, legal action. But given the volume of complaints, we ought to reconsider how we handle noise-related problems.

More forceful responses to severe noise-related conflicts include the creation of a specialized enforcement unit with the authority to look into complaints, the installation of noise sensors with permission, and the issuance of abatement orders. Although these are positive steps, given the number of cases and the current manpower shortage, will these initiatives be sufficient?

A comprehensive approach that makes use of technology ought to include defining precise noise guidelines, enforcing them, and requiring soundproofing in all upcoming building projects.

Furthermore, it might be worthwhile to think about creating simple-to-install “self-help” Internet of Things-enabled noise sensor kits for ongoing monitoring to assist impacted citizens.

People who are easily startled by loud noises may be more willing to pay the price.

Furthermore, giving residents more authority communicates to the neighborhood that proactive noise control measures are expected.

These developments could lead to a significant decrease in the need for court cases and mediation, improve community harmony, and establish Singapore as a world leader in intelligent, sustainable urban planning.

References

www.straitstimes.com

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Building Accoustics

Engineering Acoustics: Noise and Vibration Control textbook (Wiley Series in Acoustics Noise and Vibration) 1st Edition

ENGINEERING ACOUSTICS
NOISE AND VIBRATION CONTROL

A masterful introduction to the theory of acoustics along with methods for the control of noise and vibration

In Engineering Acoustics: Noise and Vibration Control, two experts in the field review the fundamentals of acoustics, noise, and vibration. The authors show how this theoretical work can be applied to real-world problems such as the control of noise and vibration in aircraft, automobiles and trucks, machinery, and road and rail vehicles.

Engineering Acoustics: Noise and Vibration Control covers a wide range of topics.

The sixteen chapters include the following:

  • Human hearing and individual and community response to noise and vibration
  • Noise and vibration instrumentation and measurements
  • Interior and exterior noise of aircraft as well as road and rail vehicles
  • Methods for the control of noise and vibration in industrial equipment and machinery
  • Use of theoretical models in absorptive and reactive muffler and silencer designs
  • Practical applications of finite element, boundary element and statistical energy analysis
  • Sound intensity theory, measurements, and applications
  • Noise and vibration control in buildings
  • How to design air-conditioning systems to minimize noise and vibration

Readers, whether students, professional engineers, or community planners, will find numerous worked examples throughout the book, and useful references at the end of each chapter to support supplemental reading on specific topics. There is a detailed index and a glossary of terms in acoustics, noise, and vibration.

From the Back Cover

ENGINEERING ACOUSTICS
NOISE AND VIBRATION CONTROL

A masterful introduction to the theory of acoustics along with methods for the control of noise and vibration

In Engineering Acoustics: Noise and Vibration Control, two experts in the field review the fundamentals of acoustics, noise, and vibration. The authors show how this theoretical work can be applied to real-world problems such as the control of noise and vibration in aircraft, automobiles and trucks, machinery, and road and rail vehicles.

Engineering Acoustics: Noise and Vibration Control covers a wide range of topics.

The sixteen chapters include the following:

  • Human hearing and individual and community response to noise and vibration
  • Noise and vibration instrumentation and measurements
  • Interior and exterior noise of aircraft as well as road and rail vehicles
  • Methods for the control of noise and vibration in industrial equipment and machinery
  • Use of theoretical models in absorptive and reactive muffler and silencer designs
  • Practical applications of finite element, boundary element and statistical energy analysis
  • Sound intensity theory, measurements, and applications
  • Noise and vibration control in buildings
  • How to design air-conditioning systems to minimize noise and vibration

Readers, whether students, professional engineers, or community planners, will find numerous worked examples throughout the book, and useful references at the end of each chapter to support supplemental reading on specific topics. There is a detailed index and a glossary of terms in acoustics, noise, and vibration.

BUY THIS BOOK
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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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Asia Noise News Building Accoustics

Govt to set up dedicated unit to resolve serious noise disputes between neighbours

Singapore neighbour noise nuisance
Singapore neighbour noise nuisance

SINGAPORE – A new unit is slated to be formed by the end of 2023 to help resolve protracted and egregious disputes between neighbours over noise disturbances.

This group will be given the power to investigate disputes and stop certain nuisance behaviour, said Senior Minister of State for National Development Sim Ann on Thursday during the debate on her ministry’s budget.

It will also have stronger laws – such as mandatory mediation under the enhanced Community Dispute Management Framework (CDMF) – to resolve “serious cases that are beyond self-help”, she added in response to Mr Yip Hon Weng (Yio Chu Kang) and Mr Henry Kwek (Kebun Baru).

Mr Kwek had highlighted disputes arising from intentional anti-social behaviour, which Ms Sim said is a serious matter the Government is closely monitoring and studying.

She noted that there is a small set of severe cases where the conflict between neighbours becomes entrenched and acrimonious.

“Often, there are signs that at least one of the conflicting parties purposely weaponised noise to cause suffering to their neighbours over a prolonged period. We think this is wrong and that strong actions are needed to put a stop to this,” she said.

The Straits Times reported in 2020 that a couple was barred from their Bukit Panjang flat for a month after they were found to have breached an earlier court order to stop disturbing their neighbours in the unit above.

The couple finally sold their flat, ending the protracted dispute that began in 2017.

It was the first time an exclusion order had been issued by the Community Disputes Resolution Tribunal (CDRT) under the State Courts.

Cases where noise is used as a weapon to disrupt the peace among neighbours will be included under the new legal framework on mandatory mediation for community disputes.

Source

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Asia Noise News Building Accoustics Building Acoustics Environment Noise and Vibration Product News Noise-th Uncategorized Vibration

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

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

Acoustic of Small Studio

Studio Acoustic

Small studios are now widely used in the recording industry due to their high feasibility and them being economically friendly, which allows those working in the recording/music industry to be able to work remotely without needing to travel to big studios that much. With a good implementation of acoustic treatments, music recorded in small studios can still be high in sound quality, sometimes even suitable for commercial release.

So, what makes a recording studio good?

In today’s article, we will look into the acoustics of small recording studios, where music is performed as recorded (Everest & Pohlmann, 2015).

Ambient conditions

A quiet environment is a must for a studio to be useful, which is sometimes quite hard to achieve. First, noisy sites should definitely be avoided as many noise and vibration problems will not arise by just choosing a site in a quiet location for your studio. Avoid places near loud areas like train tracks, busy road intersections, or even an airport. The ultimate idea is to reduce the external noise spectrum, then keep the background noise within the criteria goal by implementing sound insulations in the building. However, the construction costs of effective insulation elements like floating floors or special acoustically treated walls/windows/doors may cost greatly. Hence, the best way, that is more cost-effective, will be to choose a quiet site in the first place, rather than isolating a studio located at a noisy place.

The HVAC system, which includes heating, ventilating and air-conditioning systems should be designed such that the acoustics meet the required noise criteria goals. The noise and vibration coming from motors, fans ducts diffusers etc. should be brought to the minimum so that low ambient noise levels can be achieved.

Noise

Similar to any other quiet rooms, a small studio needs to comply with the acoustical isolation rules and standards. It is important to construct the building elements with high transmission loss and decoupled from external noise and vibration sources to ensure that the ambient noise levels are low enough for good recording quality. Not only that, but these constructions will also act as an isolation that prevents loud noise (music) levels in the studio from affecting the neighbouring spaces.

Studio acoustical characteristics

Inside a studio, the types of sound present, and may be picked up by microphones, are the direct and indirect sounds. Direct sound is basically the sound coming from the source (before it hits a surface). Indirect sound follows right after the direct, caused by various non-free field effects characteristic of an enclosed area. In short, everything that is not direct sound is considered as indirect or reflected sound.

It is known that the sound pressure level in an enclosed space will vary according to the distance from a source, while also being affected by the absorbency of the room or space. If all the surfaces in a room are fully reflective, it means that the room is fully reverberant (like a reverberation chamber), therefore the sound pressure level would be the same (as of the sound from the source) everywhere in the room as no sound energy is absorbed. It can also be assumed that there is relatively no direct sound since most of the sounds are reflected, hence indirect. Another component that causes indirect sound comes from the resonances in a room, which is also the result of reflected sound.

Indirect sound also depends on the materials used for room construction (e.g., doors, walls, windows, floors, ceiling etc). These elements can also experience the excitation by the vibration of sound from the source, hence able to decay at their own rate when the excitation is removed.

Reverberation Time

The composite effect of all the indirect sound types is reverberation. Many would say that reverberation time is an indicator of a room’s acoustical quality, but in reality, measuring reverberation time does not directly reveal the nature of the reverberation individual components, giving a small weakness of reverberation time being the indicator. Therefore, reverberation time is often not the only indicator of acoustical conditions.

Reverberation time is, by definition, the measure of decay rate, and is usually known as T60. For example, a T60 of 1 second represents that a decay of 60 dB takes 1 second to finish. Some may say that it is inaccurate to apply the reverberation time concept to small rooms, as a genuine reverberant field may not exist in small spaces. However, it is still practical to utilize the Sabine equation (for reverberation) in small-room design to make estimations on the absorption requirements at different frequencies, provided that limitations of the process are taken into account during the estimation.

It is not good to have it being too long or too short. This is because for a room with reverberation time that is too long, speech syllables and music phrases will be masked hence causing a worsening speech intelligibility and music quality. Conversely, if the reverberation time is too short, speech and music will lose character therefore suffer in quality, whereby music will typically suffer even more. Despite that, there is no specific optimal value for reverberation time that can be applied for any rooms, because too many factors are also involved besides reverberation. Things like the types of sound sources (female/male voice, speed of speech, types of language etc) will all affect the room’s acoustic outcome. However, for practical reasons, there are approximations available for acousticians to refer to, where certain amount of compromise has been implemented to make it usable in many types of recording applications.

Diffusion
A high diffusion room give a feeling of spaciousness due to the spatial multiplicity of room reflections, and it is also a good solution to control resonances effects. To create a significant diffusing effect, the implementation of splaying walls and geometrical protuberances works well. Another way will be to distribute absorbing materials in the room, which also increases the absorbing efficiency of the room apart from diffusion. Typically, modular diffraction grating diffusing elements (e.g. 2- x 4-ft units) can provide diffusion and broadband absorption, and can be easily installed in small studios. Still, there will not be much diffusion in a studio room, in practice.


Examples of acoustic treatment
So, what are the acoustic treatment elements that you can use to improve your studio? These items below can be considered (Studio, 2021):
1. Bass Traps
This is one of the most important tools to have in a studio. Bass traps are normally used to absorb low frequencies, also known as bass frequencies, but in fact they are actually broadband absorbers. This means that they are also good at absorbing mid to high frequencies too.

2. Acoustic Panels
Acoustic panels work similarly like bass traps, but rather ineffective at absorbing the bass frequencies. One thing good about acoustic panels as compared to bass traps is that since they are much thinner, they offer more surface area with less material. Therefore, acoustic panels are capable of providing larger wall coverage with less cost as compared to bass traps.

3. Diffusers
Diffusers may not be as effective as compared to bass traps and acoustic panels if used in small studios. So, this really depends on users, whether they find diffusers useful for their application.
Now, where should the acoustic treatment products be placed at?
There are three key areas of the room to be defined in this case:
– Trihedral corners
– Dihedral corners
– Walls
The priority for coverage goes from trihedral corners, dihedral corners to the walls. This is because acoustic treatments should ideally be placed at areas which have the greatest impact. At trihedral corners, for example, three sets of parallel walls converge, hence if there is absorption material located here, it catches the room modes from all three dimensions, giving three times the initial effectiveness. Same concept goes for dihedral corners and walls, but with two dimensions and one dimension respectively.

 

References
Everest, F. A., & Pohlmann, K. C. (2015). Acoustics of Small Recording Studios. In F. A. Everest, & K. C. Pohlmann, Master Handbook of Acoustics (6th Edition ed.). McGraw-Hill Education – Access Engineering. doi:ISBN: 9780071841047
Studio, E.-H. R. (2021). CHAPTER 3: The Ultimate Guide to Acoustic Treatment for Home Studios. Retrieved from E-Home Recording Studio: https://ehomerecordingstudio.com/acoustic-treatment-101/

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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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