When I introduce the topic of sound masking at tradeshows, in meetings, airports and, yes, even in elevators (my father would be proud), people almost always say “Oh, you mean white noise!”
To set the record straight: No, I don’t...at least not technically.
‘White noise’ is the term for a very specific type of sound. It has a wide range of frequencies (typically from 20 to 20,000 Hz) generally randomly produced, with equal volume across the entire range. People perceive it as ‘static’ with an uncomfortable, hissing quality. Those of you old enough to remember will understand what I mean when I say this sound is very similar to the ‘snow’ broadcast by an untuned television.
Sound masking also uses a wide range of randomly generated frequencies, but typically narrower than white noise. Masking signals are usually specified from about 100 to perhaps 6,000 Hz. Also, the volume of these frequencies isn’t equal. Rather, they follow a specified, non-linear curve developed for both effectiveness and comfort. Subjectively, sound masking is a far more comfortable sound than white noise and, when properly implemented, tends to fade into the background.
‘Pink noise’ is another term you may have heard. This sound is similar to white noise, but rather than being constant in volume, it decreases at a steady rate as frequency increases (3 dB per octave). Pink noise is less hissy than white noise, but tends to have a rumbling characteristic due the relatively louder low frequency volumes.
So, why is the term ‘white noise’ so often associated with sound masking? Because the original masking systems developed in the late 1960s and 70s used white noise generators and the name stuck. The problem is that while white noise systems were effective maskers, they were also effective irritants (due to the poor quality of the sound) that were soon turned down or off.
To be clear, I know most people aren’t thinking of the technical meaning when they say ‘white noise.’ They’re just using a term they know for ‘sound masking system’ or believe they’re interchangeable. But I continue to differentiate between the two because the negative associations with ‘white noise’ still exist, despite the fact that sound masking technology has come such a long way since those very early days.