Patent ID: 9117437
Filing Date: 2015-08-25
Classification: G10K,H04R

Abstract:
1. A reduced power noise cancelling apparatus for outputting a noise cancelling audio signal to a speaker comprising: a receiver to receive an external noise signal; a notch filter to receive the external noise signal from the receiver and to adjust the external noise signal to provide a required gain and phase response; a first pre-amplification amplifier to receive the adjusted external noise signal from the notch filter and to pre-amplify the adjusted external noise signal; a phase shifter to receive the pre-amplified external noise signal from the first pre-amplification amplifier and to produce a phase shifted output signal from the pre-amplified external noise signal, a phase polarity of the phase shifted output signal being opposite a phase polarity of the external noise signal at a hearer's ear; a second pre-amplification amplifier to receive the shifted output signal from the phase shifter and to pre-amplify the shifted output signal to a level capable of driving the speaker; and a summation unit to sum the phase shifted output signal received from the second pre-amplification amplifier and an audio input signal to produce the noise cancelling audio signal, wherein the adjusted external noise signal from the notch filter is mixed with the audio input signal and the resultant mixed signal is received by and pre-amplified by the first pre-amplification amplifier.