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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.
Download QR code; Print/export Download as PDF; Printable version; In other projects Wikidata item; ... Sound transmission class; Sound attenuator; Soundproofing
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 ...
A noise-cancellation speaker emits a sound wave with the same amplitude but with an inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference , and effectively cancel each other out – an effect which is called destructive interference .
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 instance, attenuators used with coaxial lines would be the unbalanced form while attenuators for use with twisted pair are required to be the balanced form. Four fundamental attenuator circuit diagrams are given in the figures on the left. Since an attenuator circuit consists solely of passive resistor elements, it is both linear and ...