How to Add White Noise with Sound Masking

Published: 2010-10-26

Sound Masking refers to a process where a background type of noise is uniformly dispersed in a space. The noise is designed to cut down on the ability for people to intentionally or inadvertently hear what other people are saying to each other or on the telephone.

Typical applications for sound masking systems include telephone bull pens, where lots of conversations are going on simultaneously, or offices where confidentiality is critical—doctors, lawyers, therapists, etc.

The concept behind sound masking is that human voices fall into a certain spectrum of audible frequencies. If you add sound in an appropriate frequency compatible with those vocal frequencies, human hearing and brain processing make it difficult to distinguish and articulate those voices. Essentially, you’re raising the noise floor in a signal-to-noise ratio situation.

What you’ll hear when a system is deployed is something like air moving through duct work; it’s present, you’re aware of it, but it doesn’t sound unusual or out of context.

Used in a situation where there are cubicles or walls, carpeting and tile ceilings, sound masking systems are remarkably effective at minimizing distractions from other people talking, even if they are only 20 or 30 feet away.

Installing a sound masking system is best done before the space is occupied. A typical installation will involve placing loudspeakers above the drop tile ceiling line and firing those drivers toward the ceiling. That provides more uniform dispersion of the sound masking content. If the space in which you’re installing doesn’t have a drop ceiling, fire the speakers up to the ceiling. These systems should be done using 70-volt commercial audio products, although technically they would work with 8-ohm amplifiers as well.

Installation Tips
After installing the speakers, it’s a wise practice to run your wires in such a fashion so that logical groupings can be controlled by a 70-volt volume control. The idea is to have the same level of content in every room, regardless of size. As with any commercial audio system, you’ll need to consider the number of drivers, the tap settings for each driver, the power-handling capability of the volume control and the output power of the amplifier for satisfactory, long-term performance.

It’s critical for sound masking systems to be uniformly dispersed in an office situation. Since the speakers live above the drop ceiling, it’s impossible to direct the sound specifically to one office and not the next.

When installing the system, place the volume controls, amplifiers, and tone generator in a room where the general public can’t get at it. Some amplifiers have slots in the rear for a simple tone generator; stand-alone devices are available that use DSP for elaborately tuned systems, as well as simple component-style boxes that offer much less tenability. The program material itself comes from the tone generator device.

It’s best to deploy the system when everyone else has gone for the day. Spend time walking through the space, noting level differences and then adjusting as needed. When the office staff arrives the next day, they should only notice that the ventilation fans appear to be on all the time.

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