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Two Types of Audio Distortion

June 13th Fact-of-the-Day

Audio can be distorted a variety of ways, but the two most common types of distortion in AM and FM communication systems are harmonic distortion (HD) and intermodulation distortion (IMD). (Frequency distortion is an additional common distortion in SSB systems.) Harmonic distortion changes the relative amplitudes of various harmonic components of an audio signal. It is caused by amplitude nonlinearity. Intermodulation distortion is a condition where one audio frequency component modulates another producing sum and difference frequencies that were not present in an audio input signal. The seriousness of those two types of distortion depend on their severities and to some extent on the application, but in general, intermodulation distortion tends to degrade perceived audio quality and speech-intelligibility more than harmonic distortion. ©2005 Martek International All rights reserved.

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