(under subclass 94.1) Subject matter in which the unwanted signal is either at least partially removed by processing a selected frequency or frequency band, such as by subtracting the contents of a particular frequency band from the input signal, or is overcome by preemphasis of a particular frequency or band to enhance the signal to noise ratio.
SEE OR SEARCH THIS CLASS, SUBCLASS:
83, for feedback elimination in a public address system (this is frequently done by spectral subtraction using notch filters, for example).
93, for feedback elimination in an audio system under the class definition.
94.7, for noise suppression using a signal channel and noise channel.
98+, for control of frequency characteristics in an audio signal in general, such as for equalization.
106, for compression/expansion ("compansion") systems, which achieve enhanced signal to noise ratio through compression. Preemphasis is often found with compression.
