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16 Posts in this encyclopedia categorySolid-borne sound
Solid-borne sound (also “structure-borne” sound) is defined as sound waves propagating within or on the surface of a solid medium. When these vibrations excite the surrounding air into oscillating, audible air-borne sound is the result.
Solid-borne sound attenuation/damping
Solid-borne sound attenuation is the absorption of solid-borne noise by a layer of suitable material, e.g. heavy foil, on the parts/elements where the solid-borne sound propagates. Solid-borne sound attenuation prevents the conversion of solid-borne sound into air-borne sound. For this purpose, the medium’s surface is covered with a homogeneous layer of acoustic material (adhesive fixation or other) that transforms sound energy into other energy forms.
Solid-borne sound insulation
Solid-borne sound insulation is the prevention/impediment of sound propagation using heavy and/or thick layers of suitable acoustic materials such as composite foams.
Sonic speed
Sonic speed (or: speed of sound) cs is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. The propagation speed depends heavily on the type, temperature and density of the medium. In dry air at 20°C (68°F) and 1 bar air pressure, the speed of sound is 343.2 m/s (1,126 ft/s).
Sound
Sound is defined as the mechanical vibration of an elastic medium such as air (air-borne sound), liquids (liquid-borne sound) and solid bodies (solid-borne sound). Depending on the medium, the mechanical vibrations propagate by longitudinal waves (in the direction of propagation) or transversal waves (perpendicular to the direction of propagation). The sound’s intensity diminishes with growing distance from the sound source.
Sound absorption coefficient
Sound absorption coefficient α indicates how effectively a sound absorption material attenuates the sound waves. It is calculated as the ratio of incident to absorbed sound waves in a particular frequency band. Sometimes this value may be higher than 1, which is due to the fact that in these cases the effective surface area of the absorber material is larger than its geometrical surface.
Sound bridge
The term “sound bridge” usually refers to a path of undesired sound transmission, for instance a rigid structure disrupting a sound insulation barrier. The existence of sound bridges may cancel the effect of sound insulation measures to a large extent.
Sound conditioning of rooms/Reverberation/Sound absorber
Places like restaurants, clubhouses and offices, but also rooms or staircases in private home often present quite high noise levels, making them less comfortable places to stay in. Reverberation (i.e. lingering noise) is the result of sound waves being reflected from hard surfaces (e.g. walls, ceilings or floors). The noise level in a given room can be substantially lowered by reducing the reverberation resp. the reverberation time. For this purpose, part of the room’s interior surfaces can be covered with sound-absorbing materials (e.g. acoustic foams) that absorb the sound waves instead of reflecting them.
Sound deadening
In the case of machines, appliances and vehicle components, noise emissions are often caused by the inherent vibration of the casing. Effective noise control involves sound deadening measures that minimize these vibrations. For this purpose, heavy layers are applied to the respective metal surfaces to increase their mass.
Sound insulation
Sound insulation is the acoustic shielding of a room or device in order to prevent or reduce the transmission of air-borne or solid-borne sound to neighboring spaces. The aim is to prevent the sound from propagating by using sound insulation materials to build a sound barrier around the noise source.
Sound power
Sound power W equals the total sound energy emitted by a sound source in all directions.Noise control encompasses all measures that help reduce the transmission of sound between a sound source and a target zone or recipient.
Sound pressure
Sound pressure p (an RMS value; unit: Pascal = Pa) is the local pressure deviation from the ambient pressure that sound waves cause in a compressible medium, for instance air.
Sound pressure level
Sound pressure level Lp is a logarithmic measure of the effective pressure of a sound event and hence its volume. It is measured in decibel (dB).
Sound reduction index R
Sound reduction index R is a logarithmic value that quantifies the level of sound insulation provided by building components. R depends on the frequency and angle of incidence of the sound waves. The sound reduction index describes the sound insulation capacity of a given material. It is calculated as the ratio of the total incident sound intensity to the amount of sound intensity that the material lets through. A high R value equals a low transmission factor and hence a high sound insulation effectivity.
Sound waves
Sound waves are mechanical vibrations propagating in liquids, gases and solid bodies and transporting the sound energy emitted by the sound source.
Sound/acoustic spectrum
Sound spectrum describes a sound event’s components in terms of frequency.