Sounds and Vibrations

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The properties of sound and vibrations are very closely related to those of many other phenomena, so these pages will range outside the strict interpretation of the title.  It might be worth looking at the page on Interference, which can be found by clicking on Colour in the home page Brantacan.

Sounds consist of vibrations in gases or liquids, in which the displacement, velocity and acceleration of the fluid varies with position and time in a way which is characteristic of the particular sound.  Here is a picture of a small part of a 78 rpm gramophone record - - giving some idea of the oscillations.  On such a disc the amplitudes of higher frequencies would be emphasised relative to the lower ones.  This has two advantages.  On playback, the compensating de-emphasis reduces hiss, and the amplitudes of bass notes on the disc are not in danger of causing neighbouring grooves to meet.  In fact the groove on the disc is more related to the velocity of the particles in the air than to their displacements.

Comms    Echoes

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