Patent ID: 9191739
Filing Date: 2015-11-17
Classification: G10K,H04R

Abstract:
1. A system for reducing noise caused by a plurality of rotating devices by taking in a plurality of input signals with frequencies that are related to the rotation rates of the rotating devices, and causing one or more loudspeakers to produce sounds that are at about the same frequencies as the noise and of substantially opposite phase, the system comprising: a plurality of noise cancellers, each noise canceller comprising a harmonic frequency computer that computes from an input signal a harmonic frequency and provides the harmonic frequency to a harmonic sine wave generator that generates an output sine wave, and an adaptive filter that uses a sine wave to create a noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce noise caused by the rotating devices; and an overlap detector that compares the harmonic frequencies and, based on the proximity of the harmonic frequencies, alters the operation of one or more of the adaptive filters.