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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.
where is the sound frequency in hertz (Hz), is the speed of sound in air at 20°C in meters/second, and is the length of the transmission line in meters. The complex loading of the bass drive unit demands specific Thiele-Small driver parameters to realise the full benefits of a TL design. However, most drive units in the marketplace are ...
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.
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 ...
Data acquisition hardware for acoustic measurements typically utilizes 24-bit analog-to-digital converters (ADCs), anti-aliasing filters, and other signal conditioning. This signal conditioning may include amplification, filtering, sensor excitation, and input configuration. Another consideration is the frequency range of the instrumentation.
In general, frequency components of a sound determine its "color", its timbre. When speaking about the frequency (in singular) of a sound, it means the property that most determines its pitch. [6] Higher pitches have higher frequency, and lower pitches are lower frequency. The frequencies an ear can hear are limited to a specific range of ...
Active noise canceling is best suited for low frequencies. For higher frequencies, the spacing requirements for free space and zone of silence techniques become prohibitive. In acoustic cavity and duct-based systems, the number of nodes grows rapidly with increasing frequency, which quickly makes active noise control techniques unmanageable.
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.