Sound masking works by adding a background sound to a space. This is usually because background sound levels are too low.

A simple example of a masking sound is a radio or television. Indeed, some doctors offices use a radio to create speech privacy. The sound of the radio reduces the intelligibility of the speech. It’s not perfect, but it’s better than nothing, especially in very quiet spaces.

The mechanism of masking is to increase the ambient background sound levels.

But isn’t more noise bad?

Not really. In fact adding the right sound can help the space seem quieter. This is because of the way sound works. When a space is very quiet, any sound like talking can appear loud. Have you ever been in open plan office with the “noisy talker”? The quieter the space, the more intrusive the noise. Even typing can seem annoyingly loud in a space with low background sound.

But, if set correctly, these annoying sounds (aka “peaks and troughs”) will be more difficult to hear.

A visual example of this process is below:

Simple, right? Well, hold on. A radio isn’t going to be quite as specialised at reducing the peaks and troughs, or targeting specific sounds.

Purpose-built hardware

For a more technical solution, purpose-built hardware, including loudspeakers and a sound generator, are installed into a space to produce a randomised digital sound capable of masking noise like human speech. The loudspeakers might be installed in the ceiling cavity, under the floor, or set into the ceiling.

A range of systems are commercially available, with various functions, but as well as being randomised, the system output should be capable of being shaped between 20Hz and 20kHz (eg, using an equaliser) and zoned (eg, using a zone distributor). The loudspeakers are specifically built for sound masking service—that is, not public address system speakers, which are built for a different purpose. 

Putting it together

When sound is added to a quiet (or noisy) space, this elevates the ambient background sound levels. In quiet spaces, this reduces the intelligibility of speech along with the intrusiveness of sounds. In noisy spaces, adding sound can (counter-intuitively) make a space appear quieter.

For more information on how masking can work in different spaces, check out our case studies.