Automatic gain and frequency characteristic control unit in audio device
First Claim
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1. An automatic gain and frequency characteristic control unit, comprising:
- noise detecting means for detecting ambient noise around an audio device to provide a noise detection signal;
signal detecting means for detecting an audio signal in said audio device to provide a signal detection signal corresponding to the level of said audio signal thus detected;
subtracting means for detecting a level difference between said noise detecting signal and said signal detection signal; and
gain and frequency characteristic varying means inserted in an audio signal path of said audio device to vary gain and a frequency characteristic of selected components of said audio signal according to an output signal of said subtracting means, different ones of said selected components having their frequency characteristics varied to different degrees.
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Abstract
An automatic gain control unit particularly adapted for vehicular use is disclosed. The ambient noise level inside the vehicle is detected, as is the level of the audio signal. A difference is formed between detection signals thus produced, and a frequency characteristic of a gain varying device, inserted in an audio signal path of the audio device, is varied according to this difference.
21 Citations
11 Claims
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1. An automatic gain and frequency characteristic control unit, comprising:
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noise detecting means for detecting ambient noise around an audio device to provide a noise detection signal; signal detecting means for detecting an audio signal in said audio device to provide a signal detection signal corresponding to the level of said audio signal thus detected; subtracting means for detecting a level difference between said noise detecting signal and said signal detection signal; and gain and frequency characteristic varying means inserted in an audio signal path of said audio device to vary gain and a frequency characteristic of selected components of said audio signal according to an output signal of said subtracting means, different ones of said selected components having their frequency characteristics varied to different degrees.
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2. An amplifier device, comprising:
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an operational amplifier having inverting and non-inverting input terminals and to the noninverting input terminal of which a signal is applied; a first impedance circuit connected between said inverting input terminal and an output terminal of said operational amplifier; a second impedance circuit including series-connected time constant circuits, the second impedance circuit being connected between said inverting input terminal of said operational amplifier and a reference potential; and a plurality of switching elements connected respectively between connecting points of said time constant circuits and said reference potential, wherein on-off operations of said switching elements are controlled to simultaneously change a gain and a frequency characteristic of the amplifier device. - View Dependent Claims (3, 4)
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5. An automatic gain and frequency control unit, comprising:
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audio signal level detecting means for detecting a signal level of an audio signal through a filter to produce an audio level signal according to the signal level thus detected; noise level detecting means for providing a noise level signal according to the level of noise in a vehicle; control means for providing a control signal according to said audio level signal and said noise level signal; and gain and frequency characteristic varying means responsive to said control signal for selectively emphasizing frequency components to different degrees in said audio signal. - View Dependent Claims (6, 7)
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8. An audio signal processing circuit for processing an input audio signal for production by an audio device, said circuit comprising:
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noise detecting means for detecting ambient noise around said audio device to provide a noise detection signal; signal detecting means for detecting an audio signal in said audio device to provide a signal detection signal corresponding to the level of said audio signal thus detected; means for combining said noise detection signal and said signal detection signal to generate a control signal; and
gain and frequency characteristic varying means responsive to said control signal for changing the levels of predetermined frequency components of said input audio signal to different degrees within said input audio signal. - View Dependent Claims (9, 10, 11)
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Specification