Acoustics Demystified
SANDY BROWN
in association with Shure
It’s common these days to find meeting spaces that feature the latest audio and video conferencing technology with a view to enabling the best possible meeting experience for users.
It’s common these days to find meeting spaces that feature the latest audio and video conferencing technology with a view to enabling the best possible meeting experience for users. However, one area that is often overlooked when rooms are being designed and configured is that of room acoustics.
No matter how much is spent on technology, it’s a simple fact that it’s impossible for it to entirely combat poor acoustics. However, the art of acoustic design is often perceived to be highly technical and expensive meaning it can be overlooked. With that in mind, this white paper aims to demystify acoustics by providing easy to follow detail on the questions to ask, the processes to follow and the checks to make to ensure your AV conference calls sound the best they possibly can.
Room acoustics is a broad term that describes how sound waves behave within a room. Each room, and all the objects in it, will react differently to different frequencies of sound. Factors such as the size of the space, shape, ceiling height and materials within a room will all affect its acoustics.
Larger untreated rooms are more reverberant
At short distances reverberation is not an issue
At greater distance more energy excites the reverberant field
At long distances most sound is in the reverberant field
The time required for the sound to ‘fade away’ or decay in a closed space.
The reverberation time of a room or space is defined as the time it takes for sound to decay by 60dB.
Involves either controlling intrusive noise from outside or minimising noise bleed from a room.
The loss of sound energy when sound waves come into contact with a surface or material as a result of which some sound is not reflected back into a space.
The underlying level of continuous, steady noise such as from HVAC or traffic.
The scattering of sound waves both in terms of direction and time, reducing the sense of localisation.
If an enterprise is struggling to carry out effective meetings, there are usually three main causes:
In order to avoid any or all of these issues, it’s important to employ an acoustic consultant at an early stage in any design or build project. While it is possible to troubleshoot and fix problems once the initial project is completed, retrofitting is expensive and time consuming so it’s worth investing at the start.
The three key issues to consider when it comes to room acoustics are sound insulation, background noise and reverberation/reflected sound.
It’s imperative that sound insulation is considered from day one of a project. So, for example, when architects, interior designers and building services consultants are planning the space, acoustic designers need to be involved at this stage. Decisions such as where walls are located, where rooms are positioned within a building and common services in the ceiling void can have a major impact on room acoustics, but if acoustics isn’t factored in until a later stage it can be difficult, costly and time consuming to make the necessary changes to a design to ensure good room acoustics.
Any meeting room project will have a budget and, from an acoustic point of view, it’s important that the first consideration is the sound insulation strategy.
Supplying your acoustic consultant with an overlay of the architectural drawing to show the high level structure and services can be useful as it will highlight anything that would benefit from being moved or adjusted.
Background noise in the room, meanwhile, is really important from a quality of call point of view. It’s important to remember that for a room to have good acoustics it’s all about achieving a balance. The ideal space should be quiet enough to enable participants to comfortably have a meeting but not so quiet that it suffers from intrusive noise coming into it from those working outside.
When looking at ventilation and AC systems, remember that many now focus on reducing energy usage so when you’ve got lower occupancy in the rooms they ramp down and the noise level in the room reduces. This means there can be a significant variation in the background noise level in rooms so don’t simply rely on the stated maximum noise level.
The architect will be a key part of any office design and build team. When employing an architect, take the time to find out about the team and their experience of completing similar projects. A successful project is all about the people involved so make sure there is strong leadership and that they are on hand to guide junior team members.
It’s also important that the architect considers the project in its entirety. Often, a strategy is agreed with the architect and by the time acoustic consultants are called in the layout has been fixed, meaning there is little opportunity to alter the design. This can lead to issues with acoustic treatment, which often can’t be overcome easily. The ultimate effect is that you may well end up with something that isn’t up to the standard expected. With a bit of forethought and earlier involvement an acoustic consultant can advise on space planning, adjusting partition lines or a number of other relatively simple alterations that could vastly improve the outcome of the project.
Acoustics is impacted by design, fit out and building services so consider the project in its entirety.
Services are a big part of meeting room design because they affect not only background noise levels but also sound insulation. How you run and ventilate rooms will affect how you maintain the sound insulation.
Rooms must be comfortable spaces for all users so while younger users may prefer lively acoustics, older users and those with hearing impairments are likely to struggle to understand speech in a reverberant environment and when there’s a high level of background noise. Consider the effects of a lack of acoustic finishes on people who don’t have perfect hearing and also too many sound absorbent finishes which can make rooms uncomfortable to be in for a longer period of time.
Most projects follow RIBA’s Plan of Work (see boxout). These useful guidelines lead the whole design, with the client signing off at each stage. However, a current trend is for these stages to be ignored or combined, often because programmes are shortened meaning everything has to be done to a tighter timeframe. To ensure mistakes are less likely to occur and design issues are less likely to crop up at a later stage, following these design stages is a must.
If acoustic consultants aren’t appointed until stage 3, for example, by which point the design is already at an advanced stage, yet they require changes to be made, this will potentially lead to delays and additional work for the team.
Having said that, it’s important to understand that we don’t live in a perfect world, and a good acoustic consultant will realise this and work to achieve the best possible solution within the constraints of a project. Achieving a specific reverberation time whilst maintaining the desired look and feel of the space requires careful judgement and often a degree of compromise based on experience.
According to RIBA, the Plan of Work 2013 reflects the very best principles in contemporary architectural project and design management. It organises the process of briefing, designing, constructing, maintaining, operating and using building projects into eight key stages.
STAGE 0 Strategic Definition in which a project is strategically appraised and defined before a detailed brief is created.
Design trends have a major impact on acoustics. Meeting spaces are often designed with a particular look and feel in mind and current trends include exposed soffits and high level services in offices all of which can make the room acoustics increasingly challenging due to the lack of sound absorption.
In addition, architects often desire clean, sleek, modern finishes meaning stone, timber, plasterboard, metal and concrete are frequently incorporated into designs. All of these materials reflect sound pretty much to the same extent so how you mitigate reverberation and noise build-up in spaces is increasingly important.
There have been major advances in AV technology in recent years, yet even with the algorithms and devices available, technology can only overcome poor spatial acoustics to a certain extent. If technology is constantly fighting against the reverberation it will never perform to the best of its abilities. By spending time at the beginning of a project getting the room acoustics as good as you can, you get the best out of your technology; the two should be viewed hand in hand.
One relatively recent change to the market that can help both acoustic consultants and architects is the increase in the number of architectural acoustic products on the market, many of which perform more than just an acoustical function. Take acoustic furniture solutions, for example, that simply weren’t available 10 years ago; products such as this assist the acoustics, meet the design vision and can be cost-effective. Again, it’s important to consult an acoustic specialist before choosing a solution as they will have knowledge about how these items work in real-world scenarios, rather than simply relying on the marketing material.
While it’s true that you can make a meeting work even in a room with difficult acoustics, problems occur when you introduce video/audio into the mix and you have people involved at the far end of a call as well as in the room. The effect this has on the quality of audio calls is often overlooked.
In a meeting room you need good, clear direct sound, so ideally you want people to be as close together as possible, facing each other and with a low background noise level to let your voice transfer as far as possible. But what you don’t want is much reflection from the room. When you’re in a meeting room, you can tolerate more reverberation than you can on the far end of a voice call where you’ll pick up a lot of the room response, which reduces the intelligibility of the speech that you’re hearing.
At the end of a voice call the ideal situation is a dead room – ie with very little reverberation, so for meeting rooms the aim is typically to achieve shorter reverberation times to minimise the effect of those reflections on speech intelligibility. However, this needs to be carefully balanced with the experience of those within the room itself as too much sound absorption can feel uncomfortable after a period of time.
Remember, if you’re speaking with clients and potential clients, their experience at the far end reflects on your company’s image so it’s important to consider their needs as well as those in the room.
Create a proper client briefing for your acoustic designer and involve them at an early stage in the project.
Request audio demonstrations and simulations of how spaces might sound rather than simply accepting a description in words.
Get clear explanations, without technical language. Ensure you understand what they’re talking about.
Consider how spaces will be used. Do areas need to be multifunctional, is there a requirement for recording or streaming in some rooms? If so they will need different acoustical treatments.
Budgets can be a major constraint when it comes to office design and fitout, and it can be difficult to convince those holding the purse strings that they need to spend on acoustics. One issue is that technology has moved on so much, and can represent a significant investment, so it is often seen as the solution to all problems. However, it’s important to understand that, not only will you get more from your tech in a properly designed room, but room acoustics don’t have to be expensive. When thought about in advance and considered along with the interior design of spaces there are numerous options that can make a big difference to acoustical performance but that don’t have to represent a significant financial outlay.
The role of a good acoustic consultant is to influence the design sufficiently so that spaces are ultimately fit for purpose. This doesn’t necessarily mean achieving the ideal acoustic but it does mean finding the balance between aesthetics and functionality so that rooms are comfortable, easy and reliable to use. By involving an acoustic consultant at an early stage it is possible to make major improvements to a room’s acoustics without having to spend large amounts of money, and it’s certainly a more sensible investment than trying to fix unsuitable rooms retrospectively.
Sandy Brown is one of the world’s most experienced independent acoustic consultancies. Providing advice on acoustics, noise and vibration control, the company has an extensive portfolio encompassing over 10,000 projects and is widely recognised for its expertise in building acoustics, studio acoustics and auditoria. Sandy Brown remains instrumental in driving the development of building acoustics, both in the UK and internationally.
Every voice matters. Whether it’s a keynote speech, a lecture, or a videoconference, speech intelligibility is critical to successful collaboration.
At Shure, we have over 90 years of experience enabling great communicators to command attention. We create innovative, reliable, easy to support audio solutions that support collaboration tools and seamlessly integrate into your workspace and network.
To learn how make audio work for you, please visit www.shure.com
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