A microphone for picking up speech in an enclosure typically also picks up noise from nearby equipment. A common approach to reduce such noise is to first estimate the noise and then to remove it, e.g., through cancellation or frequency sub-band damping. Noise cancellation typically involves additional hardware, e.g., additional microphone(s) to estimate noise, cancellation circuitry, etc.
Observing that noise from equipment typically present in conference rooms, e.g., computers, fans, etc., have a sharp noise spectral density, techniques of this disclosure employ notch filters, e.g., filters with sharp V-shaped reject-frequencies, to remove noise. Notch filters, having narrow reject-frequencies, effectively cut down noise and produce an audio signal that improves audio quality in audio calls.
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Lundberg, Robin, "Notch filters for removing common noise frequencies", Technical Disclosure Commons, (November 07, 2017)