Office Sound Masking Systems Explained
The architecture and layout inside modern office buildings has changed considerably in just a couple of decades, going from numerous segregated rooms to an open plan style which allows for collaborative working and communication. However, this design shift has also brought about challenges related to noise control and speech privacy. This issue has become prevalent in a variety of places, from offices and call centers through to retail stores and high street banks.
In recent years a number of psychological studies have been undertaken in office environments to gauge the need and effect of Sound Masking. In one study it was found that there is a modest stress increase and diminished motivation caused by typical office noises, including speech. According to the International Facility Management Association (IFMA), maintaining consistent background sound levels is essential for speech privacy and occupant comfort.
What is a Sound Masking System?
The solution is to install Sound Masking, which is a dedicated audio system that adds an unobtrusive background sound to reduce the intelligibility of speech from adjacent colleagues or customers. It was created to address the lack of speech privacy in open office workstations. 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.
Sound masking means controlling background sounds in a developed environment. It is significant and prioritizes modifying the background sound (in contrast to background noise); however, there is substantial evidence produced and published by Banneker (BBN) and Kavanaugh[1] indicating that acoustical satisfaction within a space cannot be guaranteed without consideration of the three principal parameters of architectural acoustical design, formalized and established in the early 1900s by Sabine.
Sound masking is an effective solution in masking intruding noise. Sound masking seeks to reduce the intelligibility of sound from a source by reducing the signal-to-noise ratio. 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.
How Does Sound Masking Work?
Sound Masking works by broadcasting white or pink noise through a speaker to reduce distractions or provide confidentiality. 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.
In order for Sound Masking to work it must reduce the difference between the steady background level and the transient levels associated with both speech and other sounds. The system capabilities must also be determined based on the amount of people in the office. The main element which you have to consider is the size and placing of the speakers which will create the white/pink noise, as well as the Sound Masking Generator.
Components of a Sound Masking System
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. The noise signal is fed from a specially designed generator and amplifier to the sound masking (SM) speakers. Sound masking speakers, generators and amplifiers are typically sold separately.
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. The plenum is the space between a "dropped" ceiling and the upper deck to the floor. In plenum sound masking systems, which employ a network of loudspeakers located completely within the plenum, were the first such systems developed and have been in use since the 1960s. 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.
What Does Sound Masking Noise Sound Like?
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.
Types of Sound Masking Systems
The right outcome depends on three levers: the masking type (direct vs. diffuse), speaker layout/spacing, and smart zoning.
- Direct-field sound masking uses downward-firing speakers for quick installs, but it often creates uneven coverage in larger offices. Direct-field systems work best in smaller offices or spaces with uniform ceilings.
- Diffuse-field systems, which send sound upward to the deck before reflecting it down, deliver more consistent results.
Classic (Analog) vs. Digital Sound Masking
- Classic (Analog) sound masking system is ideal for offices under 10,000 square feet because it’s simple, affordable, and field-tuned during setup. Analog is ideal for smaller offices under about 10,000 sq ft-it’s simple and cost-effective. Analog keeps hardware simple & labor light.
- Digital sound masking, on the other hand, is built for larger projects - offering programmable zones, remote adjustments, and integration with paging or mass-notification systems. Networked control speeds commissioning & reconfiguration.
Sound Masking Applications
Sound masking is the inclusion of generated sound (commonly, though inaccurately, referred to as "white noise" or "pink noise") into an environment to mask unwanted sound. It relies on auditory masking. 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 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.
Sound masking is applied to an entire area to improve acoustical satisfaction, thus improving the acoustical privacy of the space. Sound Masking is a highly effective way to stop people from being distracted by each other when making phone calls or having conversations within an open plan area.
Here are some typical applications:
- 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.
Designing a Sound Masking System
Good sound masking system design keeps spacing consistent and tuning balanced. Good sound masking system design keeps analog layouts efficient-consistent spacing, clean zoning, and predictable coverage. Great hardware can still flop with poor layout, missing zones, or no commissioning plan. To create a consistent background noise that reduces distractions and improves speech privacy. At Commercial Acoustics, their engineers develop sound masking layouts that balance coverage, cost, and comfort-complete with speaker counts, zoning recommendations, and stamped design documents.
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.
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.
Most offices perform best with roughly 15-16 feet between speakers, about 225 sq ft per unit. Keep on-center spacing near 15-16 ft even if the formula yields higher numbers; large floors benefit from tighter grids. Use closer spacing near reception or glass-heavy areas to avoid level dips. Plenum installs keep hardware invisible while ACT diffuses sound evenly. If budgets are tight, spacing can stretch toward 1.7 × (2D + H − 4), but uniformity drops. Over-spacing: Pushing beyond ~16 ft O.C. Leverage presets for departments with different noise profiles (sales vs. engineering).
Typically an office without Sound Masking will have an ambient sound level of under 40 decibels. An Ambient level is defined by the noise which occurs when nobody is present in the room. Conversational speech levels tend to be near 65 decibels causing conversations to be understood, and distracting to others, from up to 15 metres away.
Retrofitting Sound Masking Systems
Yes. Sound masking is one of the easiest acoustic systems to retrofit since speakers sit above the ceiling grid or on decorative mounts.