Acoustic quieting

This article primarily discusses mechanical and acoustic noise. See Noise reduction for electronic noise.
For noise masking by saturation, see Sound masking or pink noise.
For signature reduction in general see Stealth technology.

Acoustic quieting is the process of making machinery quieter by damping vibrations to prevent them from reaching the observer. Machinery vibrates, causing sound waves in air, hydroacoustic waves in water, and mechanical stresses in solid matter. Quieting is achieved by absorbing the vibrational energy or minimizing the source of the vibration. It may also be redirected away from the observer.

One of the major reasons for the development of acoustic quieting techniques was for making submarines difficult to detect by sonar. This military goal of the mid- and late-twentieth century allowed the technology to be adapted to many industries and products, such as computers (e.g. hard drive technology), automobiles (e.g. motor mounts), and even sporting goods (e.g. golf clubs[1]).

Aspects of acoustic quieting

When the goal is acoustic quietening, a number of different aspects might be considered. Each aspect of acoustics can be taken alone or in concert so that the end result is that the reception of noise by the observer is minimized.

Acoustic quieting might consider...

By analyzing the entire sequence of events, from the source to the observer, an acoustic engineer can provide many ways to quieten the machine. The challenge is to do this in a practical and inexpensive way. The engineer might focus on changing materials, using a damping material, isolating the machine, running the machine in a vacuum, or running the machine slower.

Methods of quieting

Mechanical acoustic quieting

A sound proof room, showing acoustic damping tiles used for noise absorption and soundproofing.

Quieting for specific observers

Electronic quieting

See also


  1. U.S. Patent 5,692,968
  2. "Dead Rooms and Live Wires: Harvard, Hollywood, and the Deconstruction of Architectural Acoustics, 1900-1930," Emily Thompson, Isis, Vol. 88, No. 4 (Dec., 1997), pp. 597-626. Retrieved from in November 2007.
  3. U.S. Patent 6,386,134
  4. U.S. Patent 5,090,774
  5. U.S. Patent 5,675,456
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