Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
Quality Of Sound
A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
Categories of Sound Wave
People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
A boy is standing at a railroad crossing for a track that runs east and west. As he faces the track, east is to his right and west is to his left. Two trains on the track some distance apart are headed west, both at speeds of 8.20 m/s, and blowing their whistles (which have the same frequency). One train is approaching him from the east and the other is traveling away from him toward the west. (Assume the speed of sound is 343 m/s.)
(a)If he hears a beat frequency of 8.00 Hz, determine the frequency (in Hz) emitted by the two whistles.
(b)What If? What would be the frequency (in Hz) of the beats that he hears if the lead train stops at a station (and continues to blow its whistle) while the second train continues traveling toward him?
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