The quantity x/c is the time that the wave takes to travel the distance x.
The ordinary frequency , in Hertz, of the wave can be found using
For sound waves, the amplitude of the wave is the difference between the pressure of the undisturbed air and the maximum pressure caused by the wave.
Sound's propagation speed depends on the type, temperature and pressure of the medium through which it propagates.
In an elastic medium with rigidity, a harmonic pressure wave oscillation has the form,
The force acting to return the medium to its original position is provided by the medium's bulk modulus.
Maxwell's equations lead to the prediction of electromagnetic waves in a vacuum, which are transverse (in that the electric fields and magnetic fields vary perpendicularly to the direction of propagation). However, in a plasma or a confined space, there can exist waves which are either longitudinal or transverse, or a mixture of both. In plasma waves, there exists some examples and these plasma waves can occur in the situation of force-free magnetic fields.
In the early development of electromagnetism, there was some controversy, in that Helmholtz' theory led to the prediction of longitudinal waves. Oliver Heaviside examined this problem as there was no evidence suggesting that longitudinal electromagnetic waves existed in a vacuum. After Heaviside's attempts to generalize Maxwell's equations, Heaviside came to the conclusion that electromagnetic waves were not to be found as longitudinal waves in "free space" or homogeneous media. But it should be stated that longitudinal waves can exist along the interface between differing media (such as the various layers of the Earth's atmosphere and the surface of the Earth or as in the Schumann resonance).
Maxwell's equations do lead to the appearance of longitudinal waves under some circumstances in either plasma waves or guided waves. Basically distinct from the "free-space" waves, such as those studied by Hertz in his UHF experiments, are Zenneck waves. The longitudinal mode of a resonant cavity is a particular standing wave pattern formed by waves confined in a cavity. The longitudinal modes correspond to the wavelengths of the wave which are reinforced by constructive interference after many reflections from the cavity's reflecting surfaces.
|Wave Transmission System (1940)|
|Ultrasonic Surface Waveguides (1970)|
|Surface Wave Transducer (1970|
|Longitudinal Wave Propagation Demonstrators (1970)|
|Process for eliminating longitudinal wave components in seismic exploration (1980)|
|Synthetic aperture ultrasonic testing apparatus with shear and longitudinal wave modes (1984)|
|Method and apparatus for measuring metal hardness utilizing longitudinal and transverse ultrasonic wave time-of-flight (1987)|
|Method and apparatus for measuring azimuthal as well as longitudinal waves in a formation traversed by a borehole (1992)|
|Surface acoustic wave device (1998)|
|Acoustic viscometer and method of determining kinematic viscosity and intrinsic viscosity by propagation of shear waves (2002)|
|Acousto-optic devices utilizing longitudinal acoustic waves (2003)|
|End surface reflection type surface acoustic wave apparatus utilizing waves with a longitudinal wave or shear vertical wave main component (2003)|
|Apparatus and method for minimizing electromagnetic emissions of technical emitters (2003)|
|Piezoelectric drive excited by longitudinal and flexural waves (2004)|