Waves are the result of oscillating motions which are propagated along a linear or nonlinear path, depending on the wave.
The uniform oscillations of a wave are displaced in a medium either transversely, longitudinally, or torsionally, and in various combinations, depending on the kind of wave, and the medium.
Wave motions occur in a mechanical, or fluid, medium such as a gas, liquid, or solid, or in an electromagnetic or electrochemical medium.
Acoustic waves are created by a periodic disturbance of the substance contained in a fluid medium.
Normally, an acoustic wave is a longitudinal wave which travels outward in all directions at the speed of sound, which is about 1100 feet per second at sea level, or 750 miles per hour.
An acoustic wave is characterized by an energy transfer process in which an initial vibration is generated by a source, and propagated by the transfer of energy from one vibration to the next.
Acoustic waves vibrate at frequencies ranging from tiny thermal fluctuations of the trapped particles in a sound wave, to large-scale oscillations which occur within, on, or near planetary bodies, stars, and galaxies, and include those frequencies which vibrate within the threshold of human hearing.
An acoustic wave propagates at or near the normal speed of sound, or at subsonic or supersonic speeds, depending on the thermodynamic properties of the medium in which the wave is traveling.
Acoustic waves travel faster in liquids than in gas, faster still in solids.
Electromagnetic waves are transverse waves which oscillate within a wide range of frequencies, and propagate in a narrow path at the constant velocity of light, or about 186,000 miles per second.
Electromagnetic waves oscillate at frequencies which correspond to the various wavelengths contained within the electromagnetic spectrum, including the narrow band of frequencies which produce visible light.
Unlike normal acoustic waves, the electrically charged particles in an electromagnetic wave travel with the wave, although some particles may travel slightly slower or faster than the average speed of light, depending on the conditions under which they occur.
Electrochemical waves are created by electrochemical impulses which propagate along the membranous fibers within the nervous system of living organisms, including the human brain.
Electrochemical waves carry information from the sensory organs of the body to various regions of the brain.
Electrochemical waves fluctuate within a small range of frequencies, which is the same for all sensory impulses, and propagate at subsonic speeds.
The wave paused, and then drew out again, sighing like a sleeper whose breath comes and goes unconsciously.
. . . And in me too the wave rises. It swells; it arches its back. I am aware once more of a new desire, something rising beneath me like the proud horse whose rider first spurs and then pulls him back. – Virginia Woolf