Enhancing Office Acoustics: The Benefits of Sound Masking Machines
In today's open office environments, noise distractions and a lack of speech privacy can significantly impact employee productivity and overall workplace comfort. Sound masking technology offers a viable solution by introducing a carefully engineered background sound to reduce the intelligibility of human speech. This strategic approach minimizes distractions, improves speech privacy, and supports a more conducive work environment.
What is Sound Masking?
Sound masking is the introduction of continuous, engineered background sound-often resembling gentle airflow-to reduce the perceived intelligibility of human speech. Implemented properly, a sound masking system improves speech privacy, minimizes noise distractions, and supports better workplace acoustics.
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. 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.
How Sound Masking Works
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.
The Science Behind 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.
Modern systems like Cambridge Qt use pink noise-a balanced background sound centered around the frequency range of human speech-to effectively lower speech intelligibility. 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.
Even when properly installed and tuned, a sound masking system introduces a new acoustical element in any environment. This is why upon installation, the system should be programmed to gradually “ramp up” the volume at which it operates. This helps those within sound masking’s range to become acclimated to the new background sound without disruption.
Safety and Sound Pressure Levels
Sound masking typically operates at a measured sound pressure level (SPL) of no more than 48 decibels A-weighted (dBA) in an open office. This sound masking level is significantly lower and set at 40 to 42 dBA in private offices. Such SPL levels are much lower than many common sounds, such as road noise when riding in an automobile or normal face-to-face conversation (which averages 65 dBA at three feet away).
A-weighting is a filter process used to better represent sound levels based on how humans perceive sound and is the standard for the measure of environmental noise levels.
The decibel (dB) is an expression of a logarithmic relationship; therefore, 90 dBA represents an acoustic pressure exposure more than 125 times more powerful than the 48 dBA level of typical sound masking in an open office space. It is worth noting that sound masking solutions from Biamp are not capable of producing sound levels even approaching OSHA limits. The speakers and amplifiers used in sound masking solutions are physically incapable of reaching harmful levels. Their purpose is to subtly enhance the environment, not to overwhelm it.
Regulatory Compliance
The Occupational Safety and Health Administration (OSHA) regulates safe occupational noise exposure levels in dBA SPL over time as published in Title 29 of the Code of Federal Regulations Part 1910.95. For an 8-hour period, the allowable continuous noise exposure is 90 dBA, while 80 dBA is permissible for a 32-hour period. The full details of this regulation are available here.
OSHA and ASTM are just two of the organizations that recognize sound masking as a viable, safe technology for reducing speech intelligibility and noise-related distractions, thereby improving acoustic privacy and workplace comfort and productivity.
Proper Installation and Tuning
Like all other professional audiovisual technologies, sound masking requires installation and tuning by a properly trained system integrator. A sound masking system that isn’t installed correctly-with emitters (specially engineered loudspeakers) improperly spaced or wired out of sequence, and if there are two similar output channels next to each other-could create the comb-filtering effect.
If a person is sitting precisely in the middle of those two emitters, it could potentially create an uneasiness (some refer to this as a phasing issue). But this shouldn’t create any adverse effects, and the issue can easily be addressed by installing the emitters in their proper locations.
Additional Benefits
Sound masking also protects patient confidentiality and helps patients sleep better while being treated in medical facilities. Sound masking solutions have been successfully deployed in commercial environments since the 1960s. Decades of implementation have shown no evidence that sound masking systems cause adverse health effects.
Sound Masking Levels
The following table illustrates typical sound levels for sound masking and other common sounds:
| Sound Source | Sound Pressure Level (dBA) |
|---|---|
| Sound Masking (Open Office) | 48 |
| Sound Masking (Private Office) | 40-42 |
| Normal Conversation (at 3 feet) | 65 |
| OSHA Allowable Continuous Noise Exposure (8-hour) | 90 |
| OSHA Permissible Noise Exposure (32-hour) | 80 |