SOUND PROCESSING APPARATUS AND METHOD

• US 20110142255A1
• Filed: 11/30/2010
• Published: 06/16/2011
• Est. Priority Date: 12/11/2009
• Status: Abandoned Application

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tanaka, Atsushi
• Application Number:
  US12/957,182
• Publication Number:
  US 20110142255A1
• Time in Patent Office: Days
• US Class Current: 381/94.1
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone

Abstract

A sound processing apparatus according to the present invention sets a volume value to a default value, outputs a pure tone signal of a predetermined frequency as a test signal from a loudspeaker, and acquires the output test signal using a microphone. When a signal level of a harmonic tone component of the acquired signal is equal to or greater than a threshold, the apparatus reduces the volume value so that the signal level equal to or greater than the threshold falls below the threshold and stores the reduced volume value. When outputting an acoustic signal, the apparatus adjusts a signal level of the acoustic signal at a stored frequency so that a product of a signal level at the stored frequency and a current volume value does not exceed a product of a signal level of the test signal and the stored volume value.

Claims

1. A sound processing apparatus that adjusts, based on acoustic characteristics of a reproduced sound field, a frequency response of an acoustic signal to be output, the apparatus comprising:

an outputting unit configured to output, in a state where a volume value that specifies a volume to be output from a loudspeaker is set to a default value, pure tone signals of a plurality of frequencies at respectively different timings as test signals from the loudspeaker;

an acquiring unit configured to acquire the respective test signals output by said outputting unit from the loudspeaker using a microphone;

a controlling unit configured to reduce the volume value for each of the signals acquired by said acquiring unit when a signal level of a harmonic tone component is equal to or greater than a threshold so that the signal level of the harmonic tone component falls below the threshold, and to store, in a storage unit, the reduced volume value in association with a frequency of a test signal corresponding to the signal in question; and

an adjusting unit configured to adjust the signal level of the acoustic signal at the frequency stored in said storage unit so that when outputting the acoustic signal, a product of a signal level of the acoustic signal at the stored frequency and a current volume value does not exceed a product of a signal level of a test signal at the stored frequency and a volume value stored in said storage unit in association with the stored frequency.

2. The apparatus according to claim 1, wherein said adjusting unit comprises:

a bandpass filter configured to pass only a component of a frequency stored in said storage unit among the acoustic signal;

a limiter configured to set a product of a signal level of the test signal at the frequency stored in said storage unit and a volume value stored in association with the stored frequency as a peak value and limit a signal level of the acoustic signal so that a product of a signal level of a signal passed through said bandpass filter and a current volume value is equal to or lower than the peak level;

a band elimination filter configured to eliminate a component of the frequency stored in said storage unit of the acoustic signal;

a delay circuit configured to delay an output signal of said band elimination filter so that the timing of the output signal coincides with the timing of a signal output from said limiter; and

a synthesizing unit configured to synthesize an output signal of said limiter and an output signal of said delay circuit and output an acoustic signal whose signal level at the frequency stored in said storage unit has been adjusted.

3. The apparatus according to claim 1, wherein said adjusting unit comprises:

a transform unit configured to transform the acoustic signal into a frequency-domain signal;

a reducing unit configured to reduce a spectrum value of the frequency-domain signal at a frequency of the acoustic signal stored in said storage unit when a first product of a signal level of the acoustic signal at the frequency stored in said storage unit and a current volume value is greater than a second product of the signal level of the test signal at the frequency stored in said storage unit and a volume value stored in association with the stored frequency so that the first product equals or falls below the second product; and

an inverse-transform unit configured to transform the frequency-domain signal after a spectrum value thereof has been adjusted by said reducing unit into a time-domain signal.

5. A non-transitory computer-readable storage medium storing a program that enables a computer to function as respective unit included in the sound processing apparatus according to claim 1.

4. A sound processing method for adjusting a frequency response of an acoustic signal to be output based on acoustic characteristics of a reproduced sound field output, the method comprising the steps of:

outputting, in a state where a volume value that specifies a volume to be output from a loudspeaker is set to a default value, pure tone signals of a plurality of frequencies at respectively different timings as test signals from the loudspeaker;

acquiring the respective output test signals from the loudspeaker using a microphone;

reducing the volume value for each of the acquired signals when a signal level of a harmonic tone component is equal to or greater than a threshold so that the signal level of the harmonic tone component falls below the threshold, and for storing, in a memory, the reduced volume value in association with a frequency of a test signal corresponding to the signal in question; and

adjusting the signal level of the acoustic signal at the frequency stored in the memory so that when outputting the acoustic signal, a product of a signal level of the acoustic signal at the stored frequency and a current volume value does not exceed a product of a signal level of a test signal at the stored frequency and a volume value stored in the memory in association with the stored frequency.