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Frequency Response

The Frequency Response of a filter is defined as its Gain and Phase Shift versus Frequency. When the Phase Shift is inaudible, we typically plot only the Gain versus Frequency.

For audio filters, Gain is usually plotted in decibel (dB) units (log amplitude) versus log-frequency. In other words, audio Frequency Responses are typically log-log plots. (See Weber's Law for sensory perception sensitivity.)

Mathematical Definition of Frequency Response