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Sound waves traveling through a fluid such as air travel as longitudinal waves. Particles of the fluid (i.e., air) vibrate back and forth in the direction that the sound wave is moving. This back-and-forth longitudinal motion creates a pattern of compressions (high pressure regions) and rarefactions (low pressure regions).
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Sound waves traveling through a fluid such as air travel as...
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- Overview
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sound, a mechanical disturbance from a state of equilibrium that propagates through an elastic material medium. A purely subjective definition of sound is also possible, as that which is perceived by the ear, but such a definition is not particularly illuminating and is unduly restrictive, for it is useful to speak of sounds that cannot be heard by the human ear, such as those that are produced by dog whistles or by sonar equipment.
The study of sound should begin with the properties of sound waves. There are two basic types of wave, transverse and longitudinal, differentiated by the way in which the wave is propagated. In a transverse wave, such as the wave generated in a stretched rope when one end is wiggled back and forth, the motion that constitutes the wave is perpendicular, or transverse, to the direction (along the rope) in which the wave is moving. An important family of transverse waves is generated by electromagnetic sources such as light or radio, in which the electric and magnetic fields constituting the wave oscillate perpendicular to the direction of propagation.
Sound propagates through air or other mediums as a longitudinal wave, in which the mechanical vibration constituting the wave occurs along the direction of propagation of the wave. A longitudinal wave can be created in a coiled spring by squeezing several of the turns together to form a compression and then releasing them, allowing the compression to travel the length of the spring. Air can be viewed as being composed of layers analogous to such coils, with a sound wave propagating as layers of air “push” and “pull” at one another much like the compression moving down the spring.
A sound wave thus consists of alternating compressions and rarefactions, or regions of high pressure and low pressure, moving at a certain speed. Put another way, it consists of a periodic (that is, oscillating or vibrating) variation of pressure occurring around the equilibrium pressure prevailing at a particular time and place. Equilibrium pressure and the sinusoidal variations caused by passage of a pure sound wave (that is, a wave of a single frequency) are represented in Figure 1A and 1B, respectively.
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A discussion of sound waves and their propagation can begin with an examination of a plane wave of a single frequency passing through the air. A plane wave is a wave that propagates through space as a plane, rather than as a sphere of increasing radius. As such, it is not perfectly representative of sound (see below Circular and spherical waves). A...
Figure 1C is another representation of the sound wave illustrated in Figure 1B. As represented by the sinusoidal curve, the pressure variation in a sound wave repeats itself in space over a specific distance. This distance is known as the wavelength of the sound, usually measured in metres and represented by λ. As the wave propagates through the air, one full wavelength takes a certain time period to pass a specific point in space; this period, represented by T, is usually measured in fractions of a second. In addition, during each one-second time interval, a certain number of wavelengths pass a point in space. Known as the frequency of the sound wave, the number of wavelengths passing per second is traditionally measured in hertz or kilohertz and is represented by f.
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There is an inverse relation between a wave’s frequency and its period, such that
Sound waves make the ear drum vibrate. Hammer, Anvil, Stirrup: ... Ultrasound waves are longitudinal waves just like sound waves, and they cannot pass through a vacuum. Ultrasound waves have a ...
The Physics of Waves. Waves are created when energy is transferred through a medium like water or air. There are two types of waves, transverse and longitudinal (sometimes called pressure or compression waves). When people think of waves, they often think of transverse waves. Click each video to see an example and explanation of both types.
Note that sound waves in air are longitudinal, and in the figure, the wave propagates in the positive x-direction and the molecules oscillate parallel to the direction in which the wave propagates. Figure 17.3 (a) A vibrating cone of a speaker, moving in the positive x -direction, compresses the air in front of it and expands the air behind it.
Note that sound waves in air are longitudinal, and in the figure, the wave propagates in the positive x-direction and the molecules oscillate parallel to the direction in which the wave propagates. Figure \(\PageIndex{2}\): (a) A vibrating cone of a speaker, moving in the positive x-direction, compresses the air in front of it and expands the air behind it.
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Sep 12, 2023 · Longitudinal Waves: In a longitudinal wave, particles in the medium move back and forth along the same line that the wave travels. Imagine pushing and pulling a spring; the compressions and rarefactions (tightening and loosening of the spring’s coils) move along the length of the spring, the same direction in which you pushed or pulled it.
