Ch 14 Sound


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SONIC BOOM NASA Image

There are many interesting physics concepts related to sound. Doppler shifts for objects with relative motion between
them create a perceived change in pitch for the listener. The speed of sound varies depending on material, temperature,
and density. Sound wave intensity is measured in decibels (dB) and sound waves can drive other objects into resonant vibration.

Below you will find links to some well explained major ideas that are important to check out. Sound is complex, relates to our
everyday lives in many ways, and has some complex mathematical relationships that you will be responsible for knowing.

Visit NASA's Speed of Sound Page

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Play with the Superposition of waves! SUPER cool simulation- mix your own waves, see how they add together,

and LISTEN to the sound produced! Caution... this java applet takes a couple of minutes to load, but is worth the wait!

Fourier: Making Waves
Click to Run

Learn how to make waves of all different shapes by adding up sines or cosines.
Make waves in space and time and measure their wavelengths and periods.
See how changing the amplitudes of different harmonics changes the waves.
Compare different mathematical expressions for your waves.

Sample image
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Sound Intensity - Decibels


Check out HyperPhysics EXCELLENT section on decibels and
on Sound Intensity including the Threshold of Hearing & Threshold of Pain

The following images are from HyperPhysics

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Where the numerator is actual sound intensity I and the denominator is the threshold of hearing

*For something to be perceived as TWICE as loud, the intensity actually increases by a factor of 10*
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