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How does sound propagate?
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How does sound work?
Learn what is sound, how it is produced by vibration of objects, and how it travels through different media. Explore the characteristics, speed, and effects of sound waves, and the human hearing and speech.
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Sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids. The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium.
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- Plane waves
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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
Learn how sound waves are produced by vibrations that create compressions and rarefactions in the air or other mediums. Explore the characteristics of sound waves, such as frequency, wavelength, amplitude, and speed, and how they affect our hearing and perception.
Jul 23, 2023 · Learn how sound is produced by vibrating objects that push and pull the air around them. Discover how sound waves travel through different media, such as air, water, and glass, and how they differ from light waves.
Sound energy is produced when an object vibrates. The sound vibrations cause waves of pressure that travel through a medium, such as air, water, wood or meta...
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Sep 21, 2019 · Learn how sound waves are produced by vibrating objects and how they travel through the air. Find out how your ears convert sound waves into signals and how pitch and loudness depend on frequency and amplitude.
Nov 8, 2023 · Learn how sound is produced by vibrating objects that push and pull air molecules, creating regions of compression and rarefaction. Explore the characteristics and behavior of sound waves, such as frequency, intensity, speed, and quality.
