Question

How does the sound produced by a vibrating object in a medium reach your ear?
A. Through electron transfer
B. Through the vibration of particles
C. Sound waves don’t need a medium
D. Not enough data

Answer 1

Hint: Sound is produced in a material medium by a vibrating source. As the vibrating source moves forward, it compresses the medium past it, increasing the density locally. This part of the medium compresses the layer next to it by collisions.

Complete answer:
Sound is produced when any object is set into vibrations. A vibrating tuning fork, musical instrument, ringing bear etc. Are sources producing different kinds of sound. All these vibrating bodies produce compression in the surrounding medium on a forward motion and rarefaction on a backward motion. This compression is air friction traveling in a given direction from a longitudinal wave motion in that direction. Thus sound waves are longitudinal waves which can travel through gas, liquid or solid medium. The propagation of sound waves in air can be easily understood by considering a vibration of a tuning fork.
The compression and rarefaction in a sound wave is caused due to the back and forth motion of the particles of the medium. This motion is along the direction of propagation of sound and hence the sound waves are longitudinal.

Sound waves constitute alternate compression and rarefaction pulses travelling in the medium. However, sound is audible only if the frequency of alteration of pressure is between \[20\text{ }Hz\text{ }to\text{ }20,000\text{ }Hz\]. These limits are subjective and may vary slightly from person to person. An average human ear is not able to detect disturbance in the medium if the frequency is outside this range. Electronic detectors can detect waves of lower and higher frequencies as well.

Note: The compression travels in the medium at a speed which depends on the -elastic and inertia properties of the medium. As the source moves back, it drags the medium and produces a rarefaction in the layer. The layer next to it is then dragged back and thus the rarefaction pulse passes forward. In this way, compression and rarefaction pulses are produced which travel in the medium.