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A sound attenuator, or duct silencer, sound trap, or muffler, is a noise control acoustical treatment of Heating Ventilating and Air-Conditioning (HVAC) ductwork designed to reduce transmission of noise through the ductwork, either from equipment into occupied spaces in a building, or between occupied spaces.
Acoustic attenuation in water is frequency-squared dependent, namely =. Acoustic attenuation in many metals and crystalline materials is frequency-independent, namely =. [10] In contrast, it is widely noted that the of viscoelastic materials is between 0 and 2.
In acoustics, Stokes's law of sound attenuation is a formula for the attenuation of sound in a Newtonian fluid, such as water or air, due to the fluid's viscosity.It states that the amplitude of a plane wave decreases exponentially with distance traveled, at a rate α given by = where η is the dynamic viscosity coefficient of the fluid, ω is the sound's angular frequency, ρ is the fluid ...
Architectural acoustics (also known as building acoustics) is the science and engineering of achieving a good sound within a building and is a branch of acoustical engineering. [1] 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.
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protectors help reduce acoustic flux from flowing into the ears.
Example of airborne and structure-borne transmission of sound, where Lp is sound pressure level, A is attenuation, P is acoustical pressure, S is the area of the wall [m²], and τ is the transmission coefficient. Acoustic transmission is the transmission of sounds through and between materials, including air, wall, and musical instruments.
The attenuation coefficient is = / (), following Stokes' law (sound attenuation). This effect is more intense at elevated frequencies and is much greater in air (where attenuation occurs on a characteristic distance α − 1 {\displaystyle \alpha ^{-1}} ~10 cm at 1 MHz) than in water ( α − 1 {\displaystyle \alpha ^{-1}} ~100 m at 1 MHz).
For lossy media, more intricate models need to be applied in order to take into account frequency-dependent attenuation and phase speed. Such models include acoustic wave equations that incorporate fractional derivative terms, see also the acoustic attenuation article or the survey paper.