| US 7,577,262 B2 | ||
| Microphone device and audio player | ||
| Takeo Kanamori, Hirakata (Japan); Takashi Kawamura, Settsu (Japan); and Tomomi Matsuoka, Ibaraki (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Nov. 18, 2003, as Appl. No. 10/714,857. | ||
| Claims priority of application No. 2002-333390 (JP), filed on Nov. 18, 2002. | ||
| Prior Publication US 2004/0185804 A1, Sep. 23, 2004 | ||
| Int. Cl. H04B 15/00 (2006.01) | ||
| U.S. Cl. 381—94.7 [381/92; 381/71.11; 381/94.3] | 24 Claims |
| 1. A microphone device which detects a target sound coming from a direction of the target sound, the microphone device comprising:
a signal generating section for generating a main signal indicative of a result obtained through detection with a sensitivity
in the direction of the target sound and a noise reference signal indicative of a result obtained through detection with a
sensitivity higher in another direction than in the direction of the target sound by orienting a direction of minimum sensitivity
to the direction of the target sound;
a determining section for determining whether a level ratio indicative of a ratio of a level of the main signal to a level
of the noise reference signal generated by the signal generating section is larger than a predetermined value;
an adaptive filter section including an adaptive filter, the adaptive filter section for generating a signal indicative of
a signal component of the target sound included in the noise reference signal generated by the signal generating section by
performing, by the adaptive filter, a filtering process on the main signal generated by the signal generating section, and
for learning a filter coefficient only when the determining section determines that the level ratio is larger than the predetermined
value;
a subtracting section for canceling a signal component of the target sound included in the noise reference signal by subtracting
the signal generated by the adaptive filter section from the noise reference signal generated by the signal generating section;
and
a noise suppressing section for suppressing a signal component of noise included in the main signal by using the main signal
and the noise reference signal after subtraction by the subtracting section, wherein
the noise suppressing section includes:
a noise suppression filter coefficient calculating section for calculating, based on a power spectrum of the main signal and
a power spectrum of the noise reference signal after subtraction by the subtraction section, a filter coefficient of a noise
suppression filter for suppressing the signal component of the noise included in the main signal; and
a time-variant coefficient filter section for causing the main signal to be subjected to a filtering process at the noise
suppression filter by reflecting the filter coefficient calculated by the noise suppression filter coefficient calculation
section.
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