What is Sound?
Sound is an energy form created by vibrations, which are longitudinal and mechanical in nature. These sound waves can traverse different mediums, causing changes in speed and wavelength, but not in frequency. Depending on their frequency, sound waves are categorized as infrasonic waves (0-20 Hz), audible range (20-20000 Hz), and Ultrasonics (greater than 20000 Hz).
In air, the speed of sound waves is 332m/sec. The speed is minimal in gases and maximal in solids. The speed of sound waves increases in humid conditions and with the rise in temperature. These waves can undergo reflection, refraction, and diffraction.
The relative motion between the source and object is termed as the Doppler effect, which is incredibly useful in astronomy. SONAR (Sound Navigation And Ranging) employs sound to measure the depth of the sea.
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Characteristics of Sound
Sound travels through air or other mediums as a longitudinal wave, where the mechanical vibration occurs along the direction of propagation. This can be visualized using a coiled spring; compressing several turns together to form a compression and then releasing them allows the compression to travel the length of the spring. Air can be viewed as layers, with a sound wave propagating as these layers "push" and "pull" at one another, similar to the compression moving down the spring.
A sound wave consists of alternating compressions and rarefactions, or areas of high and low pressure, moving at a certain speed. It is a periodic variation of pressure occurring around the equilibrium pressure at a specific time and place. The equilibrium pressure and sinusoidal variations caused by a pure sound wave are represented in the image.
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