Acoustic quieting

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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.

Contents

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

Quieting for specific observers

Electronic quieting

See also

Related Research Articles

Acoustics Branch of physics involving mechanical waves

Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries.

Sonar Technique that uses sound propagation

Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and SODAR is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.

Noise An unwanted sound

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Acoustical engineering

Acoustical engineering is the branch of engineering dealing with sound and vibration. It includes the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the design, analysis and control of sound.

Anechoic chamber room designed to completely absorb reflections of sound or electromagnetic waves

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Soundproofing Means of reducing the sound pressure with respect to a specified sound source and receptor

Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.

Muffler Device for reducing the noise emitted by the exhaust

A muffler or silencer is a device for reducing the noise emitted by the exhaust of an internal combustion engine—especially a noise-deadening device forming part of the exhaust system of an automobile.

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Architectural acoustics is the science and engineering of achieving a good sound within a building and is a branch of acoustical engineering. The first application of modern scientific methods to architectural acoustics was carried out by the American physicist Wallace Sabine in the Fogg Museum lecture room. He applied his new found knowledge to the design of Symphony Hall, Boston.

Prairie-Masker

Prairie-Masker is a radiated noise reduction system fitted to some western warships, including the Spruance, Oliver H. Perry, Arleigh Burke class destroyers, and the Ticonderoga class cruisers of the US Navy. The system was also installed during the 1960s on a limited number of post WWII Guppy III modified, and later diesel submarines.

Sound Transmission Class is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows and exterior wall configurations. Outside the US, the Sound Reduction Index (SRI) ISO index is used. The STC rating very roughly reflects the decibel reduction of noise that a partition can provide. The STC is useful for evaluating annoyance due to speech sounds, but not music or machinery noise as these sources contain more low frequency energy than speech.

Acoustic absorption refers to the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body. The energy transformed into heat is said to have been 'lost'.

Noise control

Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors.

Sorbothane is the brand name of a synthetic viscoelastic urethane polymer used as a shock absorber and vibration damper. It is manufactured by Sorbothane, Inc., based in Kent, Ohio.

Loudspeaker enclosure Acoustical component

A loudspeaker enclosure or loudspeaker cabinet is an enclosure in which speaker drivers and associated electronic hardware, such as crossover circuits and, in some cases, power amplifiers, are mounted. Enclosures may range in design from simple, homemade DIY rectangular particleboard boxes to very complex, expensive computer-designed hi-fi cabinets that incorporate composite materials, internal baffles, horns, bass reflex ports and acoustic insulation. Loudspeaker enclosures range in size from small "bookshelf" speaker cabinets with 4" woofers and small tweeters designed for listening to music with a hi-fi system in a private home to huge, heavy subwoofer enclosures with multiple 18" or even 21" speakers in huge enclosures which are designed for use in stadium concert sound reinforcement systems for rock music concerts.

Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.

QuietRock

QuietRock is a brand of constrained-layer damped gypsum panels manufactured in Newark, California, by PABCO Gypsum. QuietRock was developed in 2003 by Kevin Surace and Brandon D. Tinianov, the first sound-reducing gypsum wallboard panel for use in the building construction industry. QuietRock panels are engineered to increase sound transmission loss (STL) performance and, consequently, the Sound Transmission Class (STC) rating for building partitions using sound and vibration theory.

Acoustic transmission

Acoustic transmission is the transmission of sounds through and between materials, including air, wall, and musical instruments.

Noise, vibration, and harshness (NVH), also known as noise and vibration (N&V), is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks. While noise and vibration can be readily measured, harshness is a subjective quality, and is measured either via "jury" evaluations, or with analytical tools that can provide results reflecting human subjective impressions. These latter tools belong to the field known as "psychoacoustics."

Underwater acoustics The study of the propagation of sound in water and the interaction of sound waves with the water and its boundaries

Underwater acoustics is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water, its contents and its boundaries. The water may be in the ocean, a lake, a river or a tank. Typical frequencies associated with underwater acoustics are between 10 Hz and 1 MHz. The propagation of sound in the ocean at frequencies lower than 10 Hz is usually not possible without penetrating deep into the seabed, whereas frequencies above 1 MHz are rarely used because they are absorbed very quickly. Underwater acoustics is sometimes known as hydroacoustics.

Sound Vibration that propagates as an acoustic wave

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References

  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. JSTOR   237829.
  3. U.S. Patent 6,386,134 [ permanent dead link ]
  4. U.S. Patent 5,090,774
  5. U.S. Patent 5,675,456
  6. "Porous Acoustic Technology & Porous Acoustic Materials". www.porex.com. Retrieved 2017-03-24.