The cochlea (the word comes from Greek and Latin and means "spiral.") is an ingenious device for separating frequencies of sound. The stirrup is in contact with fluid (mostly water) in the snail-shaped cochlea.
#SOUNDWAVES ARE SERIES#
Acting like a series of levers, the hammer, anvil and stirrup amplify the vibrations of the drum. The hammer is connected to the inner side of the drum, and thus vibrates when the drum does. – the smallest in the body, the incus, malleus and stapes, commonly referred to (because of their shapes) as the hammer, anvil and stirrup, respectively. In solids and liquids, the speed of sound scales as the reciprocal of the square root of the density: But how do density changes in one type of medium affect the speed of sound waves? That's evident in the speeds of sound in air, water and metal. The more space between particles of some mass, the slower the speed of sound in that medium. The speed of sound in a medium is apparently proportional to the density of the medium. Sound travels at 1484 m/s in pure water, more than four times faster than through air, but not as fast as in a metal, where the atoms are even more tightly-packed. Sound travels nearly 20 times faster through a bar of aluminum than through air, for example (see the table above for some representative speeds of sounds in air, liquids and solids). In liquids and solids, the atoms and molecules are much closer together, thus the time between collisions is reduced, resulting in faster sound-wave travel. In air, those particles are widely spread out compared to the particles of a liquid or solid, so there is a time delay between collisions, resulting in a slower propagation of the wave. Sound traveling through air depends on collisions of particles. That's not too hard to understand, given the nature of a sound wave in air. Sound travels faster through liquids and solids than through air. The diagram below is another common way of illustrating compression and rarefaction in sound waves. This is in contrast to transverse waves like water waves, in which the disturbance in the medium is at right angles to the direction of travel. The disturbance is along the direction of travel. The disturbance in the medium (air) is in the same direction as the direction of the wave, so sound waves are called longitudinal waves. The distance between compression zones is the wavelength of the wave.
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A new compression zone has been formed and will continue to propagate to the right. The zones of high density gas are called compression zones and the zones of relatively low density in between are called rarefaction zones.Į.
In panels C and D, the wave continues to propagate. Particles that have received a push from the left will push on particles to the right, and the compression zone moves along. One such compression zone has been formed by a mechanical vibration on the left, and will now begin to move or propagate to the right. As a vibrating object moves, it periodically pushes on the surrounding air molecules, causing them to move and compress.ī. Sound is generated by vibration of something, like your vocal chords, a tuning fork or a piano string. Rarefaction is a region in a longitudinal wave where the particles are furthest apart.A sound wave is a periodic disturbance in a medium like air, though sound can also travel through liquids and solids - more on that later.Ī.
Figure 2 - A simple sine wave, shown as a transverse waveĬompression happens in the region in a longitudinal wave where the particles are closest together. Think of the way a slinky behaves if two people are holding each end and one person quickly sends a number of vibrations down it. In contrast, longitudinal waves have vibrations along the same axis as the direction in which the wave is traveling. Transverse waves vibrate at 90 degrees to the direction of the wave. Most waves are transverse, including light and the ripples we see on water. Sound waves are longitudinal and should not be confused with transverse waves. Figure 1 - Longitudinal sound wave showing compression (squeezing-high pressure) and rarefaction (spreading-low pressure) of air particles Each individual molecule only moves a small distance as it vibrates, which causes the adjacent molecules to vibrate in a rippling effect all the way to the ear. It's the vibrating air molecules that cause the human eardrum to vibrate, which the brain then interprets as sound.Īir molecules do not travel from the noise source to the ear. air, as it propagates away from its source.Īs sound passes through the air, the air particles move left and right due to the energy of the sound wave passing through it. A sound wave is a pressure vibration caused by the movement of energy traveling through a medium e.g.
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