AUDIO SIGNAL PROCESSING CIRCUIT

• US 20130039505A1
• Filed: 08/10/2012
• Published: 02/14/2013
• Est. Priority Date: 08/10/2011
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Kawano, Seiji
• Granted Patent: US 9,106,299 B2
• Time in Patent Office: Days
• US Class Current: 381/71.1
• CPC Class Codes: H03G 5/005 of digital signals
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H04B 1/0007 wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H

Abstract

An audio-signal-processing circuit includes: a noise-detecting unit to detect presence or absence of noise in an audio signal generated based on an output from a tuner configured to receive a broadcast signal; a low-pass filter, having predetermined phase characteristics, to pass the audio signal having a band of frequencies lower than a predetermined frequency; a high-pass filter, having the predetermined phase characteristics, to pass the audio signal having a band of frequencies higher than the predetermined frequency; first- and second-output units to multiply the signals outputted from the low-pass and high-pass filters by first and second coefficients and output the multiplied signals, respectively; an adding unit to add the signals respectively outputted from the first and the second output units; and a coefficient control unit to, when the noise-detecting unit has detected the presence of noise, decrease the second coefficient below the first coefficient.

Claims

1. An audio signal processing circuit comprising:

a noise detecting unit configured to detect presence or absence of noise in an audio signal generated based on an output from a tuner configured to receive a broadcast signal;

a low-pass filter, having predetermined phase characteristics, configured to pass the audio signal having a band of frequencies lower than a predetermined frequency;

a high-pass filter, having the predetermined phase characteristics, configured to pass the audio signal having a band of frequencies higher than the predetermined frequency;

a first output unit configured to multiply the signal outputted from the low-pass filter by a first coefficient and output the multiplied signal;

a second output unit configured to multiply the signal outputted from the high-pass filter by a second coefficient and output the multiplied signal;

an adding unit configured to add the signals respectively outputted from the first and the second output units; and

a coefficient control unit configured to, when the noise detecting unit has detected the presence of noise, decrease the second coefficient below the first coefficient.

2. The audio signal processing circuit of claim 1, wherein

the coefficient control unit is further configured to, when the noise detecting unit has detected the absence of noise after detecting the presence of noise, increase the second coefficient to a value before detection of the presence of noise.

3. The audio signal processing circuit of claim 2, wherein

the coefficient control unit is further configured to, when the noise detecting unit has detected the presence of noise, decrease the second coefficient as well as increase the first coefficient so that the second coefficient becomes smaller than the first coefficient.

4. The audio signal processing circuit of claim 3, wherein

the coefficient control unit is further configured to, when the noise detecting unit has detected the absence of noise after detecting the presence of noise, decrease the first coefficient to a value before detection of the presence of noise.

5. The audio signal processing circuit of claim 4, wherein

the low-pass filter and the high-pass filter each is a Linkwitz-Riley filter.