Patent ID: 9380386
Filing Date: 2016-06-28
CPC Classification: H04R

Claim Text:
1. A distortion sound correction complement device that regards a frequency at which distortion occurs in a speaker that outputs an output signal as a specific frequency, and a maximum signal level at which the output signal output from the speaker is not distorted at the specific frequency as a specific signal level, the device comprising: a first filter unit that performs, by using a peaking filter whose center frequency is the specific frequency, a filter process on an input signal in order to generate a correction band signal; a signal level detection unit that calculates an absolute value of amplitude of the correction band signal to perform maximum-value detection in order to detect a signal level of the correction band signal; a first lookup table unit that determines, based on the signal level detected by the signal level detection unit, a ratio of a signal level that has exceeded the specific signal level to the detected signal level as a value of a control signal; a second lookup table unit that determines, based on the signal level detected by the signal level detection unit, a correction amount that is used to amplify an overtone signal that is generated based on the specific frequency; a correction band extraction signal generation unit that multiplies the correction band signal by the control signal in order to generate a correction band extraction signal; a correction signal generation unit that subtracts the correction band extraction signal from the input signal in order to generate a correction signal; a level detection signal generation unit that calculates an absolute value of the correction band extraction signal and cuts DC components in order to generate a level detection signal; a first edge detection unit that detects a timing at which the correction band extraction signal turns positive after being negative in order to generate, as the overtone signal, an impulse train whose amplitude is 1; a first weighting unit that multiplies the overtone signal by the level detection signal in order to add weight to the overtone signal; a first phase inversion unit that inverts phase of the overtone signal to which the first weighting unit adds weight; a low-pass filter unit that performs, by using a low-pass filter, a filter process on the overtone signal whose phase is inverted by the first phase inversion unit, in order to suppress a high-frequency range signal level of the overtone signal; a high-pass filter unit that suppresses a low-frequency range signal level of the overtone signal on which the low-pass filter unit performs the filter process; a first amplification unit that multiplies the overtone signal on which the high-pass filter unit performs a filter process by gain that is calculated by adding the correction amount to an amplification initial value that is determined based on the input signal, in order to amplify the overtone signal; a second filter unit that performs, by using a filter having inverse characteristics of the peaking filter used by the first filter unit, a filter process on the overtone signal amplified by the first amplification unit in order to suppress a signal level of the specific frequency in the amplified overtone signal and thereby generate a complement signal; and an output signal generation unit that adds the complement signal to the correction signal in order to generate an output signal.