Sound Masking

Whether you call it white noise, pink noise or NC systems, sound masking is probably the only time that an acoustical consultant will admit that some noise is good.  The shift to open plan offices and demountable partitions from the traditional “private” office with gypsum board construction has created the need to raise the background sound levels in the work place (in a controlled manner) to cover over or mask distractive office noise.

The trick is to determine how much noise a person can tolerate before their concentration is disturbed. Telephone conversations in adjacent spaces, copiers, printers and impromptu hallway and water cooler conferences generate disruptive noise in the work space.  As discussed in a previous newsletter, when the background noise throughout an office space is uniform (not too loud, not too quiet) a worker’s perception of the acoustical isolation is significantly improved.  If a particular sound is covered or masked by another noise, a person will not be able to understand the quieter sound and it will not be disturbing.  A uniform background sound level can best be accomplished with a sound masking system which fills in and raises the overall noise level in the office during the quieter periods of the day.
There are a number of different ways to provide a uniform background sound level in the work space:

  • The careful design of the supply and return air diffusers systems will work for small areas.  This type of system utilizes the turbulence noise generated by air flow through the diffuser.  This method requires a very careful selection of the diffuser type, quantity, and locations. Very close coordination with the Mechanical Engineer, Architect, and Acoustical Consultant is required, along with an accurate knowledge of the final airflow requirements of the space to allow the selection of a diffuser with the proper airflow-to-turbulence noise rating.
  • Install small self-contained units (noise generators) often supplied by furniture vendors or other sales representatives.
  • Have a sound masking system designed and installed as you would any other technical system, be it electrical, mechanical or structural.

All of these systems must be properly adjusted to work.  System balancing and adjustment helps to minimize the intrusiveness of the system. Far too often, a system is installed then just turned on and not adjusted.

Systems provided by furniture supply houses or turn key pre-manufactured systems are often the worst offender of this problem and are sold as a quick fix.  These “simple” systems are often perceived by the workers as being very harsh or too loud and are usually turned off within a month of installation.

However, a well designed sound masking system will have the ability to control and adjust the background noise spectrum in many different frequency or tonal ranges.  The sound masking system will automatically change the volume over the course of the day, adjusting for quiet, early morning and late night hours as well as busy mid-day hours.  A good masking system will also provide methods to prevent tampering or unauthorized access (computer control, security lockouts, etc.).

A sound masking system makes a open plan office area more functional and acceptable than it would be without it.  However, any system that is not adjusted properly and is a major source of noise will be a problem. Unfortunately, this includes a sound masking

When a sound masking system is properly installed and adjusted, the quality of the work environment is significantly improved.

(c) Thorburn Associates 1994