Sound Masking Documentation & References

At NoiseCon 2017 in Grand Rapids, MI, Soft dB presented a scientific paper entitled Adaptive Volume Control for Sound Masking, written by Dr. Andre L’Esperance, et al. The paper demonstrates how the Adaptive Volume Control (AVC) feature, which allows the masking sound level to reactively vary between 42 and 45 dBA depending on ambient background noise, obtains similar levels of confidentiality and speech privacy compared to a sound masking system equipped only with a 45 dBA timer function.

Meanwhile, the real difference between the Adaptive Volume Control feature and the timer function for masking systems is seen in occupant acoustic comfort. A sound masking system featuring Adaptive Volume Control provides an unparallelled 50% improvement in occupant acoustic comfort during periods of moderate office activity, when compared to a timer function. Furthermore, if the upper limit of the AVC sound masking system is set to 48 dBA (CNRC-recommended upper limit) instead of 45 dBA, the level of acoustic comfort is maintained, but the confidentiality and speech privacy are improved by 15%.

At the fall 2018 InterNoise conference in Chicago, Soft dB presented a scientific study based on measurable and repeatable experiments to demonstrate the reality, beyond the marketing hype. The conclusions of the study are very interesting:

• Spatial uniformity of the masking sound is better (more uniform) with a plenum system than a direct field
• In the case of a sound masking system in a plenum space with obstruction, the spatial uniformity is still better than a direct field system

Soft dB is a world leading sound masking system supplier and excels in both approaches. Direct field sound masking speakers make sense in some office configurations where the plenum height is limited or when paging/background music functionality is required. However, for all other applications, installing the speakers inside the plenum space will typically be a better option for sound masking efficiency and comfort.

“Open plan offices have gradually become the predominant format of office space for a wide range of work activities. The main argument in favour of open plan offices is the expected reduced cost relative to closed offices with full height partitions. The cost savings may be a little reduced with the extra expense of meeting ‘acceptable’ speech privacy requirements. However, these additional costs are usually assumed to be small relative to the costs of decreased performance by distracted office workers. It is not possible to achieve ‘acceptable’ speech privacy if all office design parameters do not have near to optimum values. A successful open office should also include an optimum masking sound spectrum.”

The Acoustical Design of Conventional Open Plan Offices – Bradley, J.S

“When asked about their offices, 88% of respondents noted the quality of their work environment was important to job satisfaction and 84% reported that they accomplished their best work at the office. In fact, when asked if they would be willing to work an extra hour per day if they had a better working environment, 49% of respondents said yes.”

The 2006 US Workplace Survey – Gensler

“An ideal ambient noise level is approximately 45 dBA. If the noise level is much less, speech privacy will be substantially reduced. If it is much higher, the noise will be a source of annoyance and may reduce speech privacy because people will talk louder. The maximum noise level should therefore not exceed 48 dBA. Because it is important to achieve an ambient noise level within a very small range of levels, and because noise levels should also be evenly distributed throughout the office, this is usually best achieved using electronic masking noise. Of course, this also allows the spectrum, as well as the level, of the masking sound to be optimally set to maximize the speech privacy without undue disturbance.”

Criteria for Acoustic Comfort in Open-Plan Offices – Bradley, J. S.; Gover, B. N.