Evaluating Sound Masking Systems
Buy Sound, Not Looks!
When you're comparing masking systems made by different manufacturers, be certain you know what you're really buying. Ask yourself, what is it that I am consuming? The answer: you're consuming sound. Period.
Forget the shape of the speakers, where the controls are, how they work, how all the components look, etc. At the end of the day, you will only be concerned about the sound and how it performs.
Tips for Evaluating a Masking System's Sound
The sound from a masking system must do two — and only two — things:
- It must mask speech (giving you speech privacy) and,
- It must not be a distraction (in other words, it must produce a "comfortable" sound).
Everything else (controls, price, service, warranty, etc.) comes after. Of course, these factors are important, but if the system doesn't perform properly or sounds terrible, why buy it?
So, just what does a system need to do to accomplish both of these primary objectives?
The most reliable measure for how a masking system masks speech and creates speech privacy is the articulation index - the industry standard for speech privacy - as defined by ASTM (American Society of Testing and Materials). The Annual Book of ASTM Standards defines Articulation Index as "a computational method for predicting the intelligibility of speech for talkers and listeners," and it is measured using ASTM Test E-1130.
Jargon aside, the AI represents how well speech can be understood in a given space. AI is expressed as a decimal value between 0 (speech is unintelligible) and 1.00 (speech is easily heard and understood). To achieve speech privacy per this standard, an AI reader must read .2 or lower, indicating that 20 percent or less of the spoken word is intelligible. To achieve speech confidentiality, the reader must show .05 or lower.
Ideally, the masking system you select will attain the proper AI for speech privacy by customizing its sound to complement a number of different factors:
- The frequencies of male and female voices, and their loudness (or decibel level) at normal speaking levels
- Ambient noise in the space
- The acoustical values of the building's interior construction and furnishings (such as absorption and reflection coefficients, etc.).
Surprisingly, not all systems are on par with each other on how they produce, distribute and tune masking levels to address the three factors above. For a side by side comparision of Lencore's systems versus competing systems, contact Lencore at email@example.com.