Audio processor for use in high noise environments

• US 4,061,875 A
• Filed: 02/22/1977
• Issued: 12/06/1977
• Est. Priority Date: 02/22/1977
• Status: Expired due to Term

• Current Assignee: Paul Yanick Jr, Stephen Freifeld
• Original Assignee: Paul Yanick Jr, Stephen Freifeld
• Inventors: Yanick, Paul Jr., Freifeld, Stephen
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Kemeny, E. S.
• Application Number:
  US05/770,618
• Time in Patent Office: 287 Days
• Field of Search: 179/1 P, 179/107 R, 179/107 FD
• US Class Current: 381/72
• CPC Class Codes: H04M 1/19 Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor circuit arrangements for preventing eavesdropping H04M1/68; telephone cabinets E04H1/14

Abstract

There is disclosed apparatus for providing improved hearing acuity in the presence of high intensity background noise, such as that which exists at an industrial site.

The apparatus employs an input microphone which is adapted to receive audio information including noise from the environment. The output of the microphone is applied to an expander circuit, which functions to expand the high pass audio frequency band according to the nature and intensity of the noise. In a first mode expansion is provided at a variable ratio and threshold which are selected according to environmental noise. The expanded audio signal is applied to a compressor limiter module to reduce the level and limit the amplitude of the signal within predetermined and safe limits. The compressor limiter output signal is applied to an adjustable low pass filter, which serves further to accommodate the processed signal to a particular user and to limit the frequency range of the output signals. This low pass filter has an output applied to a linear attenuator which serves to reduce the amplitude of the processed signal depending upon the particular noise levels at the site. This output signal is applied to a speaker which is located in proximity with the ear of a user to allow him to communicate relatively normally in high noise environments. Additional modes are described which employ both expansion and compression prior to limiting.

Claims

1. Audio processor apparatus for providing protection against high intensity noise levels, while relatively restoring auditory acuity for a user with a normal hearing function in a noisy environment, comprising:

a. Means responsive to a range of audio signals including noise as propagating in an environment, for providing at an output an electrical signal indicative of said range;

b. a A high pass filter responsive to said electrical signal for substantially attenuating a given predetermined lower frequency portion of said range according to the type of noise present in said environment, to provide a limited range signal at an output;

c. Audio processing means including an expander for expanding the range of said limited signal according to the type of noise present, to provide an expanded range signal at an output;

d. Compressor means coupled to said expander and operative to limit the level of said expanded range signal;

e. Means coupled to said compressor means for providing at an output an audible signal manifesting frequency and intensity characteristics sufficient to compensate for said noise of said environment, whereby a user is provided with said audible signal to restore normal acuity.

2. The audio processor according to claim 1, wherein said means responsive to a range of audio signals comprises a microphone.

3. The audio processor according to claim 1 wherein said high pass filter has an adjustable frequency breakpoint over the range of 250 Hz to 1,500 Hz.

4. The audio processor according to claim 3, wherein said high pass filter has a variable bass roll-over between 6 to 18 db per octave.

5. The apparatus according to claim 1 further comprising, a selectable compressor module in parallel with said expander to enable compression of said expanded range signal for signal intensities above an expansion threshold.

6. The apparatus according to claim 1 wherein said expander means has a variable expansion threshold selected according to the intensity of said background noise.

7. The apparatus according to claim 1 wherein said compressor means has a variable compression ratio selected according to the intensity of said background noise.

8. The apparatus according to claim 1 further including a low pass filter having an input coupled to said compressor means for restricting the band of audio frequencies at said output, and a speaker coupled to said output of said low pass filter for providing said audible signal.

9. The apparatus according to claim 8 further including an attenuator coupled between said low pass filter and said speaker for linearly attenuating said signal applied to said speaker.

10. The apparatus according to claim 1 further including radio receiving means having an output coupled to the input of said high pass filter and means operative to apply a signal from said receiver to said filter during a given mode.

11. The apparatus according to claim 1 wherein said audio processing means has selectable attack and release times, selected according to the characteristics of said background noise.

12. Apparatus for processing an audio signal in the presence of high intensity background noise to permit a user to engage in reliable communication in high noise environments, comprising:

a. input transducing means operative to provide at an output an electrical signal corresponding to an audio signal plus noise propagating in an environment;

`b. a high pass filter responsive to said electrical signal to propagate all frequency components above a given low frequency value selected according to the noise present in said environment.

c. means coupled to said filter for expanding and compressing said signal and operative to compress said signal for a predetermined intensity level and to expand said signal for levels below said predetermined level to provide at an output a composite signal manifesting an intensity and frequency range according to said noise level;

d. limiting means responsive to said composite signal to limit the average intensity of said signal within predetermined limits;

e. output transducer means coupled to said limiting means for providing a processed audible signal which when applied to the ear of a user in said environment provides reliable auditory information.

13. The apparatus according to claim 12 wherein said limiting means includes a compressor.

14. The apparatus according to claim 12 wherein said high pass filter means is adjustable to provide a propagation of all frequencies above a range between 250 Hz to 1,500 Hz.

15. The apparatus according to claim 12 further comprising a housing having a front wall and a back wall positioned between side walls with said apparatus contained in said housing, said input transducing means located on said front wall and said back wall adapted to coact with the ear of a user to apply said audible signal to the ear of a user.

16. The apparatus according to claim 12 further comprising a low pass filter coupled to said limiting means and responsive to said signal to restrict the range of frequencies at an output of said filter, and means for attenuating said restricted range signal prior to application of the same to said output transducer means.

17. The apparatus according to claim 12 wherein said means coupled to said filter has a variable attack and release time, which time is varied according to the intensity of said audio signal.

18. The apparatus according to claim 12 wherein said output transducing means includes a speaker adapted to be positioned in proximity to the ear of a user.

19. The apparatus according to claim 12 further comprising a radio receiver for receiving transmitted program information and providing an electrical signal indicative of such information at an output, means coupling the output of said receiver to said high pass filter during a first mode and for interrupting said coupling during a second mode.

20. The apparatus according to claim 12 wherein said limiting means is adapted to limit the average intensity of said composite signal.

21. The apparatus according to claim 12 wherein said limiting means is adapted to limit the peak intensity of said composite signal.