What is Sound Masking? How does it work? And other FAQs
When we talk about noise in architecture, it is usually about its eradication. We install acoustic panels to absorb noise, partition rooms to prevent noise leakage and we plug in our earphones to block out irritating colleagues. However, there is another option to manage noise in architecture and it involves raising background sound levels by adding sound, rather than taking it away. Sometimes complete silence can be as uncomfortable as overwhelming noise.
Historically, building services systems have operated constantly in office buildings, providing a relatively consistent level of background noise. But with the development of modern systems background noise has been removed, which has some negative affects on those working within the office. The reduction in background, ambient noise has led to the development of electronic sound masking systems as a means to provide a guaranteed minimum level of background noise and privacy.
Sound masking is the introduction of ambient sound to a space to mask disruptive environmental noise. It is a growing industry within interior acoustics that has been shown to effectively mask distractive noises and increase privacy, productivity and well-being for room users.
This guide is designed to answer most of the questions about sound masking. Use the menu below to jump to the section of the guide that is most useful for you. Or look at the most frequently asked questions or the resources section to give you quick answers to your questions. If you are looking for a sound masking solution for your space, take a look at our sound masking products, or get in contact to discuss your project.
What is sound masking?
Put simply, Sound Masking is the addition of unobtrusive sound to an environment in order to ‘mask’ disruptive environmental noises, such as speech. However, in order to be effective, the sound added cannot just be any sound:
- Firstly, the sound must be random, meaning that it has no context and doesn’t transmit any information to the human ear. Whereas chirping and tweeting would convey the idea of birds to the human ear, sound masking conveys no meaning.
- Secondly, the sound is broadband (or wideband), which means the sound exists across a wide range of the audible spectrum (20 – 20,000 Hz).
Sound masking is often incorrectly referred to as white noise. While they are both random signals of different frequencies, the sound masking spectrum is shaped around the frequencies of human speech. This is how speech privacy is created by sound masking. White noise, on the other hand, is unshaped, representing the full spectrum of frequencies.
Furthermore, a correctly calibrated sound masking environment disperses sound throughout a given space, providing a consistent and dynamic sound environment. White noise, conversely, is localised and source-dependent. In other words, you can locate where the white noise is coming from, something you can’t do with sound masking.
A useful analogy to describe and explain the concept of sound masking is that of light – if someone switches a torch on in a dark room, it is very noticeable and disturbing. However, if someone switches a torch on in a bright room, you may not even notice it. This is because the light from the torch is ‘masked’ by the light already present in the room. By increasing the base level of noise in a space, other noises become less significant and less distracting.
Sound masking in the workplace
The evolution of sound masking has sprung up around two things:
- The growth of employee health, well-being and productivity as a consideration central to workplace design.
- A departure from partitioned, softly-furnished offices to open-plan, sleek and minimalist ones.
Unfortunately, open-plan, minimalist design often jeopardises worker satisfaction and productivity. Hard, reverberant surfaces such as glass and concrete – both prevalant in modern offices – propogate and reflect, rather than absorb, noise. Sound masking is an effective way to tackle this problem. Sound masking allows spaces to retain the slick, minimalist design that dominates modern office spaces, whilst creating a soundscape that allows for fewer disturbances and aids worker productivity and happiness.
Healthy, Happy Workplaces
What makes a happy and productive workplace? To answer this question we have to turn to the most important people in the office – the workers, and ask what their pain points are. One study from the University of Sydney goes a long way to answering this question for us:
Across open plan and cubicled offices the biggest complaint from workers is the lack of speech privacy. Speech privacy is the ability of an unintended individual to hear the contents of your speech. A lack of speech privacy means an increased ability for the content of your speech to be unintentionally heard by those around you.
Top three complaints of open-office workers:
Say speech privacy is their biggest concern.
Say visual privacy is their biggest concern.
Say excessive noise is their biggest concern.
Annoying office noises
This problem is two-fold, however, as just as your own speech may be overheard by others, so does the speech of others invade your own space. The primary consequence of this is a steep drop in the ability to concentrate. As Julian Treasure, the CEO of The Sound Agency, explains: “There is plenty of research that shows that the most destructive sound of all is other people’s conversations”. “We have a bandwidth for roughly 1.6 human conversations. So if you’re hearing somebody’s conversation, then that’s taking up 1 of your 1.6. Even if you don’t want to listen to it, you can’t stop it: You have no earlids. And that means you’ve just .6 left to listen to your own inner voice.”
The experience of the office worker attests to Treasure’s point, as this study from The Avanta Serviced Office Group shows.
Productivity
So we have established that office workers dislike noise and poor speech privacy more than any other workplace annoyance. But what are the consequences of this?
The answer is both well-being and productivity. Noise, whether speech or otherwise, has subtle but profound effects on workers psycholigically, behaviourally and cognitivally.
Consider some of the following evidence that noise in the workplace, particularly conversational noise, affects productivity in the workplace:
- This study in the British Journal of Psychology found that “both speech and office noise can disrupt performance on memory for prose and mental arithmetic tasks”.
- An experimental laboratory study from ICBEN found that memory and complex cognitive functions suffered in environments with poor speech privacy.
- A Cornell University experiment that measured worker cognition in varying office conditions found that workers in noisy offices “made 40% fewer attempts to solve an unsolveable puzzle” compared to their counterparts in quieter offices.
- More recently, a study commissioned by Plantronics found that a mere 1% of employees (down from 20 per cent in 2015) “say they are able to block out distractive noises and concentrate without taking extra steps in the office”.
Whether completing routine tasks, multi-tasking or conducting complex cognitive processes, excessive noise in the workplace is a productivity killer. Despite compelling evidence, and the fact that 96% of executives see productivity as “critical” to financial success, 63% of employees say they lack a quiet space to conduct focused work.
It’s not just productivity that is harmed by excessive noise in the offce, it is also the health and well-being of workers.
We know that noise at high levels is known to damage our hearing (it’s why factory workers wear industrial earmuffs), but even noise at lower levels can have subtle but real effects on our physiology, not just our ear drums:
- Research has shown that even intermittent exposure to loud noises can lead to higher long term stress hormone levels and hypertension.
- Noise can actually tire you out. As Arline Bronzaft, a former professor of psychology at Lehman College at the City University of New York states regarding noise: “Your pulse rate and blood pressure increase, your adrenaline surges; anything that puts added stress on the nervous system eventually depletes your energy.”
- A study published in The Journal of Applied Psychology found that workers exposed to prolonged noises typically found in open plan offices were less likely to make postural adjustments and were more susceptible to slumping at their workstations – risking musculoskeletal disorders.
It is clear that poor speech privacy can negatively affect our productivity, but even run-of-the-mill office noises that may seem innocuous, when prolonged and exposed to workers throughout the day, can harm us psychologically and physically.
Open Plan Offices & The Need For Sound Masking
Old style offices with cubicles and partitions have been replaced wholesale by open-flow workplaces where collaboration is encouraged through face-to-face engagement and a greater sense of proximity to colleagues. Intuitively, this seems like a worthwhile trend, but experientially we simply don’t enjoy this way of working.
Why not? Well it turns out we enjoy confidentiality, privacy and the ability to concentrate more than we thought:
- One study found that a switch to an open-place office actually led to a 56% increase in email, rather than interpersonal, communication between employees.
- The study, by Bernstein and Turban, found that overall employees spent 72% less time having face-to-face interactions with each other in the open-plan office.
- A survey from William Belk found that 58% of “high performance employees say they need more private spaces for problem solving”.
However, despite all our gripes about the burdens of open-plan office, it doesn’t look like the trend is going anywhere- in 2017 in the United States over 70% of offices had low or no-partitions. The idea is expounded by some of the world’s largest companies – Facebook’s main workspace is 10 acres of open office. Much of Apple’s $5-billion spaceship is built around the trend. That’s the bad news.
The good news is that sound masking is a perfect solution to this dilemma. Sound masking is a proven and cost-effective way for offices to retain their open-plan, aesthetic designs while reducing the radius of distraction that employees face in open work spaces.
How sound masking solves the open-office problem
Sound masking is an effective, cost-efficient solution to solve the biggest complaint of the modern office worker – speech privacy.
Adding unobtrusive sound into an office reduces the intelligibility of human speech and facilitates greater speech privacy and reduces distracting noises. Sound masking does not eradicate disruptive noises, but rather it ‘drowns’ obtrusive noises out.
By shaping the sound masking sound to match the spectra of noise in a given office, the distractive noises are effectively masked. Doing this reduces the radius of distraction that workers are exposed to. Typically, sound masking reduces the radius of distraction to 15 feet, meaning conversations more than 15 feet away become unintelligibile.
Improvement in ability to focus.
Reduction in perceived stress
Improvement in work errors & inaccuracies
The efficacy of sound masking has been the subject of a number of studies over the years. The results of these studies unanimously point to the benefit of sound masking for cognition and productivity in offices:
- This study from the journal of the European Acoustics Association compared five different sounds and their effects on worker performance in offices. It found that the use of “constant masking sounds”, such as running water, when compared with other sounds such as instrumental and vocal music, improved worker satisfaction and productivity.
- Another study from Sweden concluded that sound masking, when compared to the use of headphones to drown out background noises, has a positive correlation on worker memory recall tasks.
- An independent review from The Remington Group found that sound masking led to a : 48% improvement on the ability to focus, a 27% reduction in worker stress levels and a 10% improvement in errors and inaccuracies in work tasks.
Implementation
What are the sound masking components?
By BobChan2 [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons
Sound masking systems use a combination of components to achieve an effective sound masking environment. These include:
- Masking Generator: The generator is the source of the random electrical signals.
- Spectrum Equaliser: The spectrum equaliser converts the electrical signals to be accessible by the human ear.
- Mixer: The signals are then passed onto a mixer, where the appropriate levels for the signals are set.
- Amplifiers: The mixer passes the signals onto the amplifiers, which increase the signals’ amplitude.
- Zone Controllers: The amplified signals are then passed either onto speakers or to special devices that control the transmission of the signals into user-defined zones within the building or space.
- Speakers: Speakers then transmit the signals to the users in the form of white or pink noise. Or:
- Vibrators: The signals are passed onto a vibration exciter, which uses physical structures, such as plasterboard, to transmit the sound.
Each space in an office has different acoustic needs. For instance, a busy open-plan space would require greater sound masking volume than a quieter enclosed private office. Sound masking systems tackles this problem using zoning control. Each ‘zone’ is treated as its own acoustic environment, which allows the user to control the level of sound masking to match the requirements of each space.
The requirements of a space are also dictated by the surface finishes. For instance, a room with glass walls and a concrete ceiling will propogate noise and creater a louder environment than a room with absorbant carpet and curtains. This is what is called acoustic room response.
Acoustic room response dictates zoning requirements as speakers in more reverberant space should not be connected to the same channel as speakers in a less-reverberant space as the acoustic response would be differ between the two spaces
Follow these three rules when desiging a sound masking project:
As a general rule of thumb the maximum distance between speakers should be around 6 yards (or 18 feet). However, the placement and number of speakers you use for your sound masking project will depend largely on the type of ceiling in your space. Additionally, the size of the plenum will also determine the number of speakers you need as small plenums don’t distribute sound as liberally as tall plenums. Soft dB provide calculations for using their sound masking speakers with a range of different ceiling conditions:
For plenums:
Open ceilings:
For plenums taller than 6 feet:
To find a full list of calculations see Soft dB’s guide here.
Conclusion
Sound masking is an evergrowing field in the world of architectural acoustics. Often lumped in with white noise, sound masking is a unique and effective way to reduce distractions in offices and other commercial environments. Unlike white noise, sound masking is the introduction of unobtrusive, broadband sounds, which are shaped to the human hearing spectrum. Sound masking effectively drowns out the most disruptive noises that affect focus, productivity, happiness and well-being of the users of architectural space.
Sound masking is most commonly used in open plan offices. The advent of open, collaborative work-spaces has inadvertently led to an explosion of distractive noises that have invaded the spaces where we most need to concentrate and be productive. Estimates for the concentration crisis suggest we can be up to 66% less productive due to the popularity of open-plan office design. Fortunately, we don’t have to put back up the partitions; sound masking provides an effective acoustic solution to restore speech privacy and aid worker productivity. By ‘masking’ the most distracting noises, such as speech, sound masking can reduce the radius of distraction the average worker is exposed to.
Additionally, sound masking may have therapeutic benefits for tinnitus sufferers and may help to improve sleep quality, particularly for in-patients in hospitals.
The implementation of sound masking must include a number of considerations, including: zoning and room types, the type of speakers used, effective and accurate distribution of speakers to avoid ‘hot’ and ‘cold’ spots, correct implementation depending on ceiling type, among many more.
If you are planning on your own sound masking projects then it is advised to use a professional to avoid incorrect configuration and ineffective sound masking environments.