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On the other hand, acoustic wave equations based on fractional derivative viscoelastic models are applied to describe the power law frequency dependent acoustic attenuation. [18] Chen and Holm proposed the positive fractional derivative modified Szabo's wave equation [11] and the fractional Laplacian wave equation. [11]
The speed of sound (i.e., the longitudinal motion of wavefronts) is related to frequency and wavelength of a wave by =.. This is different from the particle velocity , which refers to the motion of molecules in the medium due to the sound, and relates to the plane wave pressure to the fluid density and sound speed by =.
A sound wave propagates through a material as a localized pressure change. Increasing the pressure of a gas or fluid increases its local temperature. The local speed of sound in a compressible material increases with temperature; as a result, the wave travels faster during the high pressure phase of the oscillation than during the lower pressure phase.
Historically, reverberation time could only be measured using a level recorder (a plotting device which graphs the noise level against time on a ribbon of moving paper). A loud noise is produced, and as the sound dies away the trace on the level recorder will show a distinct slope. Analysis of this slope reveals the measured reverberation time.
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, [6] and transverse sound waves (shear waves) in solids. An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular to each other. Different ...
This effect is responsible for guided propagation of sound waves over long distances in the ocean and in the atmosphere. In the atmosphere, vertical gradients of wind speed and temperature lead to refraction. [1] The wind speed is usually increasing with height, which leads to a downward bending of the sound rays towards the ground.
In air at atmospheric pressure, these represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimeters (0.67 in). Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.
In an ideal tube, the wavelength of the sound produced is directly proportional to the length of the tube. A tube which is open at one end and closed at the other produces sound with a wavelength equal to four times the length of the tube. A tube which is open at both ends produces sound whose wavelength is just twice the length of the tube.