Technical Library

Understanding Operable Wall Acoustics

A wall acoustics primer created by Hufcor Laboratories, a nationally accredited NVLAP laboratory.

The following is an online version of Hufcor's Freedom From Distraction brochure that reviews the important concepts of wall acoustics and how they relate to operable partitions. If you would like a printed copy of the brochure, please contact your local branch.

Sound is an energy which is generated by a source, transmitted through a medium, and received by a receiver.

For example, a piano string vibrates when the key is struck, generating sound. The vibration alternately compresses and expands the surrounding air, transmitting the sound in waves of pressure changes. When the waves reach your ear, you receive the sound. If you take away any of the above conditions, there is no sound. There's no sound in space, for example, since no medium exists to transmit sound waves (the explosions in space movies are unrealistic).

Sound has several measurable components:

1. Frequency
2. Amplitude
3. Duration

Let's look at them in more detail.

FREQUENCY is the rate of vibration, determining how high or low the pitch is. Frequency is measured in cycles per second, or Hertz (Hz). The wave length associated with a given frequency is the distance the sound travels in one cycle. It is related to the frequency like this:

Wave Length = Speed of Sound / Frequency

Healthy children can hear from 20 to 20,000 Hz, but the human ear is most sensitive in the range of 100 to 5000 Hz. In this range most of our music, speech, and other important sounds are found.

AMPLITUDE is the magnitude of the vibration, which determines how loud the sound is. In the piano example, the size of the change in air pressure would determine the amplitude. Amplitude (or loudness) is measured in decibels (dB), which can range from the threshold of hearing at 0 dB to the threshold of pain at around 140 dB.

DURATION is the time the sound lasts, measured in seconds. The duration may indicate how long the source is vibrating or how much the sound is reverberating, or echoing. Some sound levels will cause immediate damage to an unprotected ear. But often damage will be caused only if the duration of the sound is too long.