Study Material of Physics on Sound / SSC CGL & CHSL Exam Tier 1 2018
Study Material of Physics on Sound:
Sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain.Humans can hear sound waves with frequencies between about 20 Hz and 20 kHz. Sound above 20 kHz is ultrasound and below 20 Hz is infra sound. Other animals have different hearing ranges.
the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave’s shape repeats, and thus the inverse of the spatial frequency. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape.The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.
The delay is proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single reflection of the sound source.
Reverberation is the collection of reflected sounds from the surfaces in an enclosure like an auditorium. It is a desirable property of auditoriums to the extent that it helps to overcome the inverse square law drop off of sound intensity in the enclosure.
The human ear responds to sounds with frequencies in the range from 20 Hz to 20,000 Hz. This is called the audible range of the human ear. Examples of vibrating sources that produce sound in the audible range of frequencies are drums, guitar strings, tuning fork, human vocal cords and diaphragms of loudspeakers.
In audible sound waves whose frequencies are less than 20 Hz are in the infrasonic range. Sources of infrasonic waves include earthquakes, thunder, volcanoes and waves produced by vibrating heavy machinery. The hearing ranges of elephants and whales extend into the infrasonic region.
Frequencies above 20,000 Hz are in the ultrasonic range. The audible range of dogs, cats, moths and mice extends into ultrasound frequencies. They can hear very high frequencies that humans cannot.
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