Defining Comfort for Quality Sound Masking
HEADQUARTERS: Woodbury, NY
OBJECTIVE: Identify, measure, and use viable metrics to define whether or not comfort has been achieved by a sound masking system.
Some say comfort is subjective, but when it comes to sound masking there are viable metrics that can be identified, measured, and used to define whether comfort has been achieved or not. Acoustical comfort for sound masking can be measured by the following five qualities: the audio distribution range of the sound that is initially generated, produced, and distributed; the uniformity of the sound masking throughout the entire space; the wraparound of the generated sound; the target dB level; and finally, the privacy measurement achieved.
Audio Spectrum Distribution Range
In much the same way as with light, a quality sound masking system must have a full broadband spectrum. This quality is a driving factor when it comes to comfort. To provide acoustical comfort, a sound masking system must be able to produce and distribute a minimum spectrum range of 65hz to 16khz.
The sound’s uniformity has a huge impact on comfort in two primary ways. First, since the smallest variance that a normal human ear can perceive is approximately one dB of sound, a sound masking system with a tuning capability of +/- ½ dB will give you a tighter tolerance and therefore a more uniform field of sound. A successful and comfortable sound masking system must be able to achieve a +/- one dB overall level for uniformity.
Next, comfort is impacted by the design and layout of the speakers used to distribute the sound masking. When sound is distributed evenly throughout an environment, the space exists in acoustical harmony. If the sound distribution is spotty, or there is an uneven level of sound, the space becomes distracting. This happens because your ear continually has to adjust to the variances of the sound levels due to uneven levels of the frequency dispersion. To be comfortable, speakers must be uniformly distributed throughout an environment. Additionally, speaker orientation must be carefully considered.
How often a sound repeats, or “wraps around,” affects comfort levels. All audio masking systems have a repeat, but the differentiator here—and what we need to strive for—are sound repeats that are spaced as far apart as possible, so that the brain will not be able to “tune in” to the repeat and eventually fatigue. To ensure a comfortable sound masking system, choose one with a long repeat.
Target dB Level
A sound masking system must maintain a target ambient sound level and have a proper and measurable sound level to speech level ratio. When done right, this creates acoustical comfort because it crushes (minimizes) the acoustical dynamic range and improves privacy (by raising the ambient background sound levels). For reference, a typical masking system in an office should have ambient sound levels at 47dBA. If it provides less than 45dBA, privacy won’t be achieved. Greater than 49dBA, and masking is typically intrusive. It’s a delicate balance.
For acoustical comfort, let’s not forget that we need to have privacy in our space. A masking system intended to be used for privacy must meet standards for privacy such as ASTM E1130. By using a standard, we can ensure that the masking system levels are appropriately tuned and set.
Jonathan Leonard, president of Lencore Acoustics, has been involved in the commercial real estate, acoustics, construction, architectural and facility management industries for over 20 years.