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Sound wave theory 06
Phase and harmonics

Level of challenge Intermediate


Welcome to this tutorial on phase relationships in complex sound waves.


So far we have only looked at the simplest vibration, a sine wave. But almost all sounds are far more complex, especially those produced in nature. Complex soundwaves are formed from multiple individual vibrations, or sine waves, arriving at different times and of different frequencies.


Each individual vibration in a complex wave is known as a harmonic.


Caption - What is phase?

Phase in complex soundwaves, refers to the relationship between these harmonic vibrations, and it is essential for an understanding of how harmonics combine to create a single overall complex wave.


Caption - In phase signals

When two identical harmonics meet they produce a wave that is the sum of their amplitudes, stronger and louder. This is true for air pressure sound-waves and electrical and digital sound-waves in an electronic audio system such as a studio.


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Caption - Out of phase signals

If one of the harmonics is the mirror image of the other, or is delayed in time by half a wavelength, they are said to be out of phase and completely cancel each other out.


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Caption - Expressing phase relationships

These phase relationships can be expressed more precisely in degrees. 2 in-phase signals are said to have a phase relationship of 0 degrees, whilst 2 completely out of phase signals have a phase relationship of 180 degrees.


© Project Studio Handbook 2013 - present day


© Project Studio Handbook 2013 - present day


Both these situations represent the extremes of phase relationships. Between these extremes it is possible to have situations where the two soundwaves are partially in and out of phase.


© Project Studio Handbook 2013 - present day


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