Essentials of Effective Speech Privacy: Quieter Sound Masking
Reduced Volume with Increased Privacy
Anyone can guarantee speech privacy in an office space by simply cranking up the volume. For example, if we moved your open office format to the area adjacent to a runway, the noise would be loud enough to cover any and all distracting noises. The obvious drawback to this scenario is that the runway noise itself becomes a problem.
The spatial and spectral uniformity delivered by the VoiceArrest™ Speech Privacy System permits its operation at substantially lower sound levels than competitive systems while maintaining masking effectiveness. While other sound masking systems must be operated at 48-51 dB in a well-designed open plan office in order to provide acceptable privacy conditions for most occupants, the VoiceArrest™ Speech Privacy System is normally operated at 45 dB under the same conditions.
A frequent comment by users experienced with plenum-based masking systems is that the VoiceArrest™ Speech Privacy System “is not loud enough” to provide good speech privacy. Yet objective comparative standard measurements of the Articulation Index clearly demonstrate that VoiceArrest™ is at least as effective as louder plenum-based systems. The result is dramatically reduced acoustical obtrusiveness and user awareness of the system.
When it comes to achieving speech privacy, it’s vital to understand that competing sound masking systems – adjusted to the same volume levels – don’t necessarily deliver the same privacy levels. The individual frequencies that make up the masking sound’s spectrum determine its masking effectiveness, and to objectively measure the level of privacy provided by a given spectrum, an Articulation Index (or AI) is used.
World-renowned acoustician Leo Beranek identified the ideal sound masking spectrum for achieving speech privacy, and all sound masking systems attempt to tune the spectrum within these frequency ranges. Some octave bands have a greater impact on speech privacy than others do. The VoiceArrest™ Speech Privacy System was designed to deliver more energy in the octave bands that contribute the most to speech privacy (1000Hz, 2000Hz and 4000Hz) and less energy in the lower frequency bands (125Hz, 250Hz and 500Hz) that contribute significantly less to masking speech. The result is substantially lower sound levels than competitive systems while still maintaining masking effectiveness.
Why Doesn’t the Competition Use the Same Frequency Settings?
The reason indirect field systems can’t adjust their systems to this more efficient speech privacy spectrum relates back to the issue of speaker placement. Because their speakers are located in the plenum, they must use large speakers to generate much higher levels of sound in order to provide enough volume when it filters into the workspace below. These larger speakers produce a certain amount of energy in the lower frequency bands that simply can’t be tuned out. This lower frequency energy adds to the total volume of their system with little impact on speech privacy. So, while their spectrum can be adjusted to fall within the recommended range, it cannot deliver as much privacy per decibel of sound.
The VoiceArrest™ Speech Privacy System is a Direct Field system that radiates sound directly into the target space using very small, ultra-wide dispersion speakers. This allows us to pre-tune our spectrum for maximum speech privacy with the least possible volume.
Consistent volume levels don’t necessarily equate to consistent privacy levels.
Ready to find out how the VoiceArrest™ Speech Privacy System can raise the privacy levels of your workplace? Contact one of our acoustic consultants today!