B. Decibels

Signal processing engineers often need to measure the amplitude difference between two signals. For example, an engineer might need to compare the amplitude of a signal at the output of an amplifier to the amplitude of that signal at the input of the amplifier. Comparing the amplitude of those two signals describes the gain (the amount of amplification) of the amplifier. In practice, however, because various signals have such a wide range of amplitude values to be compared, engineers find it convenient to use decibels to simplify their numerical comparisons. This appendix describes how this is done.

The use of decibels is an expedient mathematical method for comparing the amplitude, or power, difference between two signals or between ...

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