A shock mount or isolation mount is a mechanical fastener that connects two parts elastically to provide shock and vibration isolation.
Isolation mounts allow equipment to be securely mounted to a foundation and/or frame and, at the same time, allow it to float independently from it.
Shock mounts are found in a wide variety of applications.
They can be used to isolate the foundation or substrate from the dynamics of the mounted equipment. This is vital on submarines where silence is critical to mission success. Yachts also use shock mounts to dampen mechanical noise (mainly transmitted throughout the structure) and increase comfort. This is usually done through elastic supports and transmission couplings. [1]
Other common examples are the motor and transmission mounts used in virtually every automobile manufactured today. Without isolation mounts, interior noise and comfort levels would be significantly different. Such shock and vibration-isolation mounts are often chosen by the nature of the dynamics produced by the equipment and the weight of the equipment.
Shock mounts can isolate sensitive equipment from undesirable dynamics of the foundation or substrate. Sensitive laboratory equipment most be isolated from shock from handling and ambient vibration. Military equipment and ships must be able to withstand nearby explosions.
Shock mounts are found in some disc drives and compact disc players, where the disc and rainy agreement are held by soft bushings that isolate them from outside vibration and other outside forces, such as torsion. [2] In this case, isolation mounts are often chosen by the sensitivity of the equipment to shock (fragility) and vibration (natural frequency) and the weight of the equipment.
For shock mounting to be effective, the input shock and vibration must be matched. A shock pulse is characterised by its peak acceleration, duration, and shape (half sine, triangular, trapezoidal, etc.). The shock response spectrum is a method for further evaluating mechanical shock. [3]
Shock mounts used to isolate entire buildings from earthquakes are called base isolators.
A similar idea, also known as a shock mount, is found in furniture design, introduced by Charles and Ray Eames. It provides some shock absorption and operates as a living hinge, allowing the seat back to pivot.
Shock mounts are also sometimes used in bicycle saddles, [4] handlebars and chassis.
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. [5]
One common type of isolation mounts is laminated pads. Generally, these pads consist of a cork or polymeric foam core which has been laminated between two pieces of ribbed neoprene sheet.
Molded rubber isolation mounts are typically manufactured for specific applications. The best example of this is automotive engine and transmission mounts. Rubber bushings compress synthetic rubber rings on bolts to provide some isolation – operating temperature is sometimes a factor. 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. Temperature is a factor in the dynamic response of rubber. Generally, a molded rubber mount is best suited for heavy loads producing higher frequency vibrations.
Cable mounts are based around a coil of wire rope fixed to an upper and lower mounting bar. [6] [7] When properly matched to the load, these mounts provide isolation over a broad frequency range. They are typically applied to high performance applications, such as mounting sensitive instrumentation into off-road vehicles and shipboard.
Coil spring isolation mounts generally provide the greatest degree of movement and the best low frequency performance. They are particularly popular for mounting equipment in buildings such as air handlers, filtration units, air conditioning and refrigeration systems and large pipes. Their degree of movement makes them ideal for applications where high flexure and/or expansion and contraction are a consideration.
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.
Early microphones used a 'ring and spring' mount, where a single rigid ring was mounted and carried the microphone between a number of coil springs, usually four or eight. When early microphones were heavy and omnidirectional, this was adequate. However the single plane of suspension allowed the microphone to twist very easily; once microphones started to become directional, this twisting caused fading of the signal. A more three-dimensional and less planar suspension would be required.
Large side-address studio microphone are generally strung in "cat's cradle" mounts, using fabric-wound rubber elastic elements to provide isolation. While the elastic elements can deteriorate and sag over time, the low price of the mount and ease of replacing the elastic elements mean they remain a mainstay despite introduction of elastomer-based designs less sensible to degradation over time.
The same occurs for end-fire microphones, most often employed for location work, however positioning consistency issues in mobile contexts means elastomer-based alternatives have made more inroads: they offer more displacement (positional flexibility) along the prime axis, but better restrict movement along other axis, and have less tendency to keep oscillating after movements, which provide for better control of the microphone's precise position.
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
A microphone, colloquially called a mic, or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors.
A shock absorber or damper is a mechanical or hydraulic device designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy which is then dissipated. Most shock absorbers are a form of dashpot.
Soundproofing is any means of impeding sound propagation. There are several basic ways to reduce sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles for absorption, or using active antinoise sound generators.
A torsion spring is a spring that works by twisting its end along its axis; that is, a flexible elastic object that stores mechanical energy when it is twisted. When it is twisted, it exerts a torque in the opposite direction, proportional to the amount (angle) it is twisted. There are various types:
In materials science and continuum mechanics, viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like water, resist shear flow and strain linearly with time when a stress is applied. Elastic materials strain when stretched and immediately return to their original state once the stress is removed.
A bushing or rubber bushing is a type of vibration isolator. It provides an interface between two parts, damping the energy transmitted through the bushing. A common application is in vehicle suspension systems, where a bushing made of rubber separates the faces of two metal objects while allowing a certain amount of movement. This movement allows the suspension parts to move freely, for example, when traveling over a large bump, while minimizing transmission of noise and small vibrations through to the chassis of the vehicle. A rubber bushing may also be described as a flexible mounting or antivibration mounting.
An optical table is a vibration control platform that is used to support systems used for laser- and optics-related experiments in science, engineering and manufacturing. The surfaces of these tables are designed to be very rigid with minimum deflection so that the alignment of optical elements remains stable over time. Many optical systems require that vibration of optical elements be kept small. As a result, optical tables are typically very heavy and incorporate vibration isolation and damping features in their structure. Many use pneumatic isolators that act as mechanical low-pass filters, reducing the ability of vibrations in the floor to cause vibrations in the tabletop.
A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring. The process and instrumentation diagram (P&ID) symbol for a dashpot is .
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.
Vibration isolation is the prevention of transmission of vibration from one component of a system to others parts of the same system, as in buildings or mechanical systems. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Active vibration isolation involves sensors and actuators that produce disruptive interference that cancels-out incoming vibration.
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. The latter tools belong to the field psychoacoustics.
Package cushioning is used to protect items during shipment. Vibration and impact shock during shipment and loading/unloading are controlled by cushioning to reduce the chance of product damage.
The impulse excitation technique (IET) is a non-destructive material characterization technique to determine the elastic properties and internal friction of a material of interest. It measures the resonant frequencies in order to calculate the Young's modulus, shear modulus, Poisson's ratio and internal friction of predefined shapes like rectangular bars, cylindrical rods and disc shaped samples. The measurements can be performed at room temperature or at elevated temperatures under different atmospheres.
LORD Corporation is a diversified technology and manufacturing company that develops adhesives, coatings, motion management devices, and sensing technologies for industries such as aerospace, automotive, oil and gas, and industrial. With world headquarters in Cary, North Carolina, LORD has approximately 3,100 employees in 26 countries and operates 19 manufacturing facilities and 10 R&D centers worldwide. As of October 30, 2019, the company has been acquired by Parker Hannifin.
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.
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. Vibration may be deterministic if the oscillations can be characterised precisely, or random if the oscillations can only be analysed statistically.
On maritime vessels, noise and vibration are not the same but they have the same origin and come in many forms. The methods to handle the related problems are similar, to a certain level, where most shipboard noise problems are reduced by controlling vibration.
Shock-mitigating suspension seats are designed to reduce the severity of vibration and mechanical shock. These seats are used in vehicles that operate in high exposure environments, such as high-speed watercraft, military platforms, construction, forestry and agricultural vehicles, and industrial trucks. A vehicle's collisions with waves or rough terrain are a source of whole body vibration that may cause discomfort, acute injuries, and chronic pain among operators. The marine environment is particularly severe and people exposed to these conditions may experience unusually high injury rates.
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