How Sound Masking Systems Work: Enhancing Privacy and Reducing Distractions
Sound masking is a technology used mainly in office spaces to reduce distractions and protect privacy. It is the inclusion of generated sound into an environment to mask unwanted sound. Sound masking means controlling background sounds in a developed environment. It relies on auditory masking.
Sound masking is applied to an entire area to improve acoustical satisfaction, thus improving the acoustical privacy of the space. It is significant and prioritizes modifying the background sound (in contrast to background noise). Sound masking is not a form of active noise control (noise cancellation technique); however, it can reduce or eliminate the perception of sound.
A sound masking system can be used to reduce the impression of intruding sound (reducing annoyance, distraction) and improve acoustic privacy (including speech privacy). Sound masking seeks to reduce the intelligibility of sound from a source by reducing the signal-to-noise ratio.
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Adding sound to a space actually makes the space seem quieter. It sounds counter-intuitive but it’s true. This is because the added sound reduces the intelligibility of human speech. Sound masking is an ambient sound, similar to the sound of airflow, that’s specifically engineered to the frequency of human speech you can target conversational distractions and make them less distracting. Unlike white noise, sound masking is specifically engineered to match the frequencies of human speech and to sound comfortable, even pleasant, to the human ear.
By adding a subtle, ambient sound, similar to airflow, through strategically placed speakers, it elevates the background noise level, making it harder to overhear conversations. Sound masking makes surrounding conversations and common noisy distractions a lot less audible.
Originally used only in offices and call centers, sound masking now benefits visitors and employees alike in hospitals, medical and dental clinics, bank branches, military facilities, libraries, hotels, and a whole host of other applications. In many environments that require speech privacy, employee concentration, or both, there’s simply not enough background sound (also called ambient sound), leaving occupants trying to work in a pin-drop environment. In fact, the background sound level in most offices is so low you can easily hear conversations and noise from up to 50 feet (15 meters) away.
These distractions make it difficult to concentrate. It takes more effort to focus, which tires you out, affecting your mood and, ultimately, your productivity. What’s more, confidential conversations can easily be overheard, making employees and visitors nervous about talking.Sound masking addresses these problems.
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Sound masking reduces the need for specialty acoustic insulation and extra drywall layers in closed rooms requiring good acoustic privacy. Modern workspaces are designed for collaboration, but open layouts often mean more distractions. Without proper noise control, productivity and privacy take a hit. A low-frequency, consistent sound that blends naturally with ambient noise. The sound is designed to be unnoticeable-just a subtle background hum that masks distractions.
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Sound masking systems are often relied upon as a basis of design with Sound Transmission Class (STC, as supported by ASTM E336) or Noise Isolation Class (NIC, as supported by ASTM E336) to ensure an appropriate level of privacy between contiguous rooms. Various organizations (ASTM, ASA/ANSI, GBI, LEED, ASHRAE, WELL, etc.) define unique categories for labeling acoustical zones with purpose and/or function.
Applications of Sound Masking
Sound masking is effective in a variety of settings:
- Open office plans - open offices can be either too quiet (where someone dropping a pen in the next cubicle is distracting) - or too noisy (where the conversations of others in the office make it impossible to concentrate).
- Private offices - private offices and other enclosed spaces often appear to provide privacy but do not. Many times, walls are lightweight and do not extend to the ceiling deck, but only to the ceiling tile. In these cases, sound can easily travel through partitions or over the walls.
- Public spaces - sound masking is useful for reception areas, pharmacies, waiting rooms, and financial institutions. Sound masking is provided in the area where conversations should not be heard - not necessarily in the area where the conversation is taking place. For instance, a psychiatrist would not want those in the waiting room to overhear a private conversation with a patient, so sound masking is provided in the waiting area, but not in the psychiatrist's office.
Sound masking is used in various environments to improve acoustic privacy and reduce distractions.
Several cases exist where sound masking has been successfully installed for exterior applications, the most common target of concern being roadway noise. In one example application, a large artificial waterfall was constructed as part of the garden exterior of an urban hotel in Santa Rosa, California.
Components and Types of Sound Masking Systems
At its most basic, a sound masking system consists of a series of loudspeakers installed in a grid-like pattern in the ceiling, as well as a method of controlling those speakers’ output. The loudspeakers distribute an engineered background sound, raising the facility’s ambient level in a highly controlled fashion.
Typically, these speakers are positioned out of sight above ceiling tiles in plenum space, although speakers are sometimes used in open architecture truss type ceilings. Sound masking speakers, generators and amplifiers are typically sold separately.
The plenum is the space between a "dropped" ceiling and the upper deck to the floor. Plenum-based speakers typically range 4-10 inches (10-25 cm) in diameter and generally face upwards, towards the upper deck. This is done to reflect sound from the speakers to broaden, as much as possible, the footprint from the speaker in the work area. As with any commercial-grade sound masking system, an in-plenum sound masking system requires proper layout design, commissioning, and verification of the performance. Disregarding the importance of any of these stages in implementation will result in a sound masking system that does not perform according to the specifications of an acoustician.
Only the most sophisticated sound masking systems can control the background sound level and spectra of masking sound accurately and precisely throughout a space, made possible only with the smallest zones (spatial limits around a speaker) and sophisticated electronics and software. Uniformity can be achieved by adjusting the acoustic output of individual or a small groups of speakers. Adjustments routinely include changes in the output volume and output spectra of individual speakers.
Diagram of a typical sound masking system setup.
Direct field sound masking systems have been in use since the late 1990s. The name takes after the mechanics of sound transmission which considers the "direct sound path" from the loudspeaker emitted towards the recipients (listeners) underneath. Initially used as an accessory for open office cubicles, direct field systems have been fully integrated into at least one open office furniture system and have been designed to be installed both in dropped ceilings and in offices without any absorptive ceiling systems.
When installed in dropped ceilings, direct field systems use speakers that are mounted facing down. When a ceiling tile is not available, they are mounted facing down on any available structure, sending the masking noise directly into the intended space. Theoretically, a direct field system would benefit from speakers that are omnidirectional, meaning that they transmit energy equally in essentially all directions. However, direct field systems require tighter arrays of loudspeakers given the polarity of the emission of sound.
Benefits of Sound Masking
- Noise control
- Speech privacy
- Improved productivity
- Lower project costs
- Facility flexibility
- Quick ROI
What is a sound masking system? In general, the purpose of a sound masking system is to provide for greater conversational privacy (and therefore improved productivity for those not involved in the conversation) in an open office environment by adding ambient noise and shaping the noise signal to mask speech. The noise signal is fed from a specially designed generator and amplifier to the sound masking (SM) speakers.
Many people believe electronic sound masking systems cancel unwanted sounds but that’s not the case. Unlike technology used in some headphones (which cancels unwanted sounds in the confined space of an ear muff), that technology does not work on the scale of an open room. Instead electronic sound masking systems add ambient noise to an open area. A specially filtered audio signal, described by the NC-40 Contour, increases ambient noise to effectively mask speech, making it more difficult to be understood.
Understanding Sound Masking Noise
Electronic sound masking systems are often called “white noise systems” or “pink noise systems” but neither term is technically correct. White noise (for audio use) is defined as “equal sound energy at each frequency over the usable audio spectrum.” Pink noise is defined as “equal sound energy per octave over the usable audio spectrum.”
By definition an octave is a doubling of frequency, so between 20Hz and 40Hz is an octave, between 40Hz and 80Hz is an octave, and so on. That means that compared to white noise, pink noise has much less energy in higher frequencies than it does at lower frequencies. Since human ears work in a logarithmic manner, pink noise sounds flat to the human ear, while white noise sounds overly bright. In other words, because of the nature of human hearing, to us it sounds like pink noise has as much energy in low frequencies as high frequencies even though that is really not the case.
A sound masking system doesn’t use white or pink noise but instead incorporates a very specific filtered noise (described by the NC-40 Contour) that has been proven scientifically to produce the maximum speech-masking effect.
The Sound of Sound Masking
Sound masking systems add a controlled ambient sound to reduce office noise, improve speech privacy, and create a more productive work environment. By generating a consistent background sound, these systems help block distracting noises and make conversations less intelligible to others.
The sound masking “sound” has most often been compared to softly “whooshing” air, although it’s actually a specifically engineered blend of frequencies that’s perfect for covering up speech and incidental noises. You may have experienced something like the sound masking effect when running water at the kitchen sink while trying to talk to someone in the next room. You can tell the other person is speaking, but it’s difficult to comprehend what they’re saying because the running water has raised the background sound level in your area.
Examples are endless: the sound of an airplane engine, rustling leaves, the murmur of a crowd in a busy restaurant. All of these have the potential to mask sounds you would otherwise hear.
How LogiSon® Sound Masking is Different
Of course, when introducing a masking sound to your workplace, it’s vital to ensure that it’s as comfortable and unobtrusive as possible. That’s why the LogiSon Acoustic Network uses small adjustment zones of one to three loudspeakers and offers fine control over both volume and frequency. More control means the sound will be more effective at providing masking, while easily blending into your environment.
It is used for privacy in certain environments or to avoid distractions for example in large office environments. Sound masking is often used in open offices where there is generally lots of noise going on, therefore the main reason for sound masking in offices is to avoid distraction from the noise level. As well as the typical overcrowded office situation, another common use of Sound Masking is in high street banking, pharmacies and meetings rooms.
The technology used in a Sound Masking system usually consists of a dedicated Sound Masking Generator which is a device that you install in the area you want to mask. Both white noise and pink noise cover all the frequencies that the human ear can hear, however the intensity of pink noise decreases as the frequency increases.
Most PA systems or background music systems don't have as much uniformity as you need for a sound masking system. Conventional loudspeaker systems for example have combfiltering whereby you notice a gap as you walk through. With sound masking you don't have combfiltering it is a direct field, you tend to use more than one channel.
The type of loudspeakers to use ultimately depends on if you are on a direct field system whereby you are using a type of speaker that goes into the ceiling. Then they need to be on the correct centers according to the dispersion and the room height. If you are on a plenum system, (where the speakers are above the ceiling) ceiling has perforated metal tiles for example you need to bring it in closer.
As the number of people in a room varies in a day so does the noise level. Most sound masking systems you can schedule when they come on and off. There are also some that go up and down adaptively however, this is very difficult to manage. For example it may be louder in one area so the level is brought up but in another area it is quiet and the rasing then becomes noticed.
Factors to consider include:
- Ceiling Type - Look at the type of ceiling - is it open or closed?
- Ceiling Height - Very low or high ceiling?
- Materials in ceiling - Is it perforated metal that performs like an open ceiling?
- Tuned - Is it tuned? The frequencies are different, the gaps in music and frequencies change.