Shock mount

Condenser microphone with shock mount

In a variety of applications, a shock mount is a mechanical fastener that connects two parts elastically. They are used for shock and vibration isolation.

Design

Rubber bushings compress synthetic rubber rings on bolts to provide some isolation. Other shock mounts have mechanical springs or an elastomer (in tension or compression) engineered to isolate an item from specified mechanical shock and vibration. Some form of dashpot is usually used with a spring to provide viscous damping. Viscoelastic materials are common. Maxwell and Kelvin–Voigt models of viscoelasticity use springs and dashpots in series and parallel circuits respectively. Hydraulic and pneumatic components can be included, depending on the use.

Microphone mount

Shock mounts for microphones can provide basic protection from damage, but their prime use is to isolate microphones from mechanically transmitted noise. This can originate as floor vibrations transmitted through a floor stand, or as "finger" and other handling noise on boom poles. All microphones behave to some extent as accelerometers, with the most sensitive axis being perpendicular to the diaphragm. Additionally, some microphones contain internal elements such as vacuum tubes and transformers which can be inherently microphonic. These are often cushioned by resilient internal methods, in addition to the employment of external isolation mounts.

Traditionally the large side-address studio microphone has been strung in a "cat's cradle" mount, using fabric-wound rubber elastic elements to provide isolation. These designs still find some favour, although the elements tend to deteriorate, and sag with time. Newer designs, such as Rycote's "USM" lyre [4], use plastic elastomers, and patented spring shapes to reduce this problem.

For end-fire microphones, most often employed for location work, similar elastic stringing was once used. More recently designs moved to o-ring elements, before the Rycote Lyre [5] and Cinela Osix [6] suspensions were introduced. These use spring element designs that give far greater displacement along the microphone's prime axis, while limiting it on the other two. This enables excellent isolation while retaining good control of the microphone.

[4]http://www.reddingaudio.com/rycote-invision-studio.php [5]http://www.ips.org.uk/files/11_Rycote_Lyre_Suspensions.pdf [6]http://www.cinela.fr/catalog.php?pid=6

Mounting machinery

Machinery may have flexible mounts to help control vibration and reduce noise. Automobile engines usually have flexible mounts to reduce operating noise.

Naval ships have special shock mounts to minimize machinery noise being transmitted to the water. The shock mounts help protect the shipboard operating equipment from the shock of explosions.

Disc drives

Shock mounts are found in some disc drives and compact disc players, in which soft bushings are all that mechanically hold the disk and reading assembly, thereby isolating it from outside vibrations and from other outside loads such as torsion.

Other

One of two shock mounts holding the back of the Eames Lounge Chair Wood (LCW). The black rubber is glued to the wood and the bolt only connects the metal to the rubber. There are three similar shock mounts supporting the seat.

Shock mounts can be found in a wide variety of applications.

A similar idea, also known as a shock mount, is found in furniture design, introduced by Charles and Ray Eames. This provides some shock absorption and serves as a living hinge, allowing the seat back to pivot.

Shock mounts are also used in bicycle seats.

See also

• Bushing
• Vibration isolation
• Shock absorber
• MIL-S-901
• Microphonism
• Cushioning

References

• DeSilva, C. W., "Vibration and Shock Handbook", CRC, 2005, ISBN 0-8493-1580-8
• Harris, C. M., and Peirsol, A. G. "Shock and Vibration Handbook", 2001, McGraw Hill, ISBN 0-07-137081-1

External links

• Shock and vibration testing of shock mounts [1]