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Monday, 25 July 2011

Q+A: Basic Sound Questions...

This is going back to basics with what is sound anyway?...


What is sound and how is it created?
Sound is a vibration and/or a wave of air molecules caused by motion of an object. This wave is a compression wave where the molecules are bunched up like a wave in the sea, A sound wave is created when a series of these pressure changes/waves move through the air. This wave or waves speed depends on the temperature, e.g. at 15 degrees Celsius the speed is 340.276 m/s but at 25C the speed is 346.13 m/s. (Calculator here).


Through solids the wave will bounce back or echo/reverberate and the energy can change from acoustical to electrical energy which is how microphones and telephones are able to work.


What is frequency?
When drawing a sound wave, like with any wave there is a peak and a valley which vary in distance from each other. Sound sources vibrate at different rates or frequencies as they move through the air. We measure frequency in cycles per second or Hertz. This is named after Heinrich Rudolf Hertz (February 22, 1857 – January 1, 1894) who was a German physicist who was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect VHF or UHF radio waves.
The faster an object vibrates the higher the frequency and thus higher the pitch of the sound. a common example is a tuning fork for A above middle C will vibrate at 440 times per second and so has a frequency of 440 Hertz.




What is amplitude? 
We already understand by now that sound is made by pushing air molecules together in varying degrees of strength, this is amplitude. for example if something is struck really hard the wave will carry some of that energy through the air and it will sound louder than if it is struck gently. Sound waves with the same frequency can have different amplitudes.


Feel free to add any comments if i haven't covered anything in enough detail.


Thanks,


- Matt Price

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