Electronic audio device and method of operation

• US 5,771,297 A
• Filed: 08/14/1995
• Issued: 06/23/1998
• Est. Priority Date: 08/12/1994
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Richardson, Julian Howard
• Primary Examiner(s): Harvey, Minsun Oh
• Application Number:
  US08/514,546
• Time in Patent Office: 1,044 Days
• Field of Search: 381/56, 381/57, 381/58, 381/59, 381/96, 381/104, 381/107, 381/108
• US Class Current: 381/57
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits

Abstract

An electronic audio device, such as a radio having an audio loudspeaker is described, as well as a method of operation of such a device. The device has an audio stage (6) having an audio output for providing an audio output signal, an acoustic transducer (12) coupled to the audio output for outputting an acoustic signal and a microphone element (13) acoustically coupled to the acoustic transducer to provide a feedback signal representative of the output of the acoustic transducer. A comparison circuit (15) compares parameters of the audio output signal and parameters of the feedback signal; and a control circuit (16, 24, 50) responsive to the comparison circuit controls the audio stage when a parameter of the feedback signal differs from that parameter of the audio output signal by a predetermined amount.

Claims

1. An electronic audio device comprising:

an audio stage having an audio output for providing an audio output signal;

an acoustic transducer coupled to the audio output for outputting an acoustic signal;

a microphone element with selectable gain, acoustically coupled to the acoustic transducer to provide a feedback signal representative of the output of the acoustic transducer;

a comparator coupled to the audio stage and the microphone element for comparing parameters of the audio output signal and parameters of the feedback signal;

a control circuit responsive to the comparator for controlling the audio stage when a parameter of the feedback signal differs from that parameter of the audio output signal by a predetermined amount;

a microphone gain switching element for increasing the gain of the microhone element for monitoring of ambient noise and decreasing the gain for provision of the feedback signal; and

a volume control element for controlling the audio output signal responsive to the control circuit to reduce the volume of the acoustic signal when the difference between the feedback signal parameter and the audio output signal parameter indicates distortion in the audio output signal.

2. A device according to claim 1, further comprising an ambient noise monitoring element responsive to the feedback signal for controlling the audio stage to increase the volume of the audio output signal with increased ambient noise and decrease the audio output signal with decreased ambient noise.

3. A device according to claim 1, comprising a switching element for switching between provision of the feedback signal and ambient noise monitoring as a function of activity in the audio device.

4. A device according to claim 3, wherein the switching element is arranged to switch with changes of the output signal, to provide the feedback signal when there is a significant output signal and to monitor ambient noise when there is no significant output signal.

5. A device according to claim 2, comprising an integrator element for controlling the audio stage responsive to ambient noise changes over a relatively long time period and to control the audio stage responsive to the feedback signal over a relatively short period of time.

6. A device according to claim 2, wherein the frequency profile of the audio output signal is controlled responsive to the feedback signal.

7. A device according to claim 6, wherein lower frequencies of the audio signal are attenuated relative to higher frequencies when the parameter of the feedback signal differs from the parameter of the audio output signal by a predetermined amount.

8. A device according to claim 1, further comprising a storage element coupled to the comparator for storing control parameters, responsive to the feedback signal, wherein the control circuit is arranged to recall selected parameters for later control of the audio stage.

9. An electronic audio device comprising:

an audio stage having an audio output for providing an audio output signal;

an acoustic transducer coupled to the audio output for outputting an acoustic signal;

a microphone element acoustically coupled to the acoustic transducer to provide a feedback signal representative of the output of the acoustic transducer;

a comparator for comparing parameters of the audio output signal and parameters of the feedback signal;

a storage element coupled to the comparator;

a control circuit responsive to the comparator for controlling the audio stage when a parameter of the feedback signal differs from that parameter of the audio output signal by a predetermined amount; and

a training audio output signal generator responsive to the control circuit for passing a training audio output signal to the audio stage, wherein the control circuit is arranged to cause control parameters to be stored in the storage element in response to the feedback signal provided by the microphone element when the training audio output signal is generated.

10. A method of operation of an electronic audio device comprising the steps of:

providing an audio output signal to an audio stage having an audio output and outputting an acoustic signal from an acoustic transducer coupled to the audio output;

receiving a representation of the acoustic signal at a microphone element and providing a feedback signal representative of the output of the acoustic transducer;

comparing parameters of the audio output signal and parameters of the feedback signal;

controlling the audio stage when a parameter of the feedback signal differs from that parameter of the audio output signal by a predetermined amount;

increasing the gain of the microphone element for monitoring of ambient noise and decreasing the gain for provision of the feedback signal

controlling the audio output signal to reduce the level of the acoustic signal; and

when the difference between the parameters of the feedback signal and the parameters of the audio output signal indicates distortion in the audio output signal.