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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 ...
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.
Absorption of low frequency sound is weak. [7] (see Technical Guides – Calculation of absorption of sound in seawater for an on-line calculator).The main cause of sound attenuation in fresh water, and at high frequency in sea water (above 100 kHz) is viscosity.
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.
It is based on the ASTM E-1332 Standard Classification for Rating Outdoor-Indoor Sound Attenuation. [37] Unlike the STC, which is based on a noise spectrum targeting speech sounds, OITC uses a source noise spectrum that considers frequencies down to 80 Hz (aircraft/rail/truck traffic) and is weighted more to lower frequencies.
The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. [1]
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.
c is the speed of the sound waves traveling in the medium; δ is the particle displacement; x is the space variable along the direction of propagation of the sound waves. This equation is valid both for fluids and solids. In fluids, ρc 2 = K (K stands for the bulk modulus);