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.
You are standing on a train station platform as a train goes by close to you. As the train approaches, you hear the whistle sound at a frequency of f1 = 93 Hz. As the train recedes, you hear the whistle sound at a frequency of f2 = 75 Hz. Take the speed of sound in air to be v = 340 m/s.
(a) Find an equation for the speed of the sound source vs, in this case it is the speed of the train. Express your answer in terms of f1, f2, and v.
(b) Find the numeric value, in meters per second, for the speed of the train.
(c) Find an equation for the frequency of the train whistle fs ("s" is for "source") that you would hear if the train were not moving. Express your answer in terms of f1, f2, and v.
(d) Find the numeric value, in hertz, for the frequency of the train whistle fs that you would hear if the train were not moving.
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