Patent US4083031A successfully refreshed from Google Patents.
US4083031A
Expired / Lapsed
US
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Acoustic presence detection method and apparatus
Assignee: United States Department of the Navy
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Filing: 1970-07-23
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Granted: 1978-04-04
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Expires: 1990-07-23
Abstract
Abstract A method and means for passively detecting presence of noise radiating dees in a noise environment by determining the number of times per time sample that a received noise signal upwardly crosses a preselected threshold level, comparing this number with the number of upward crossings caused by a standard noise signal or background noise signal, and applying a predetermined ratio criteria. The noise sensors in the detection system may comprise a directional acoustic transducer in combination with an omnidirectional acoustic transducer, and acoustic transducer in combination with an artificially generated noise signal, or a single acoustic transducer.
Inventors
- 👤 Lawrence C. Pharo, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 09:10
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/001; G01H; G01H3/00; Y; Y10; Y10S; Y10S367/00; Y10S367/901
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
324 words
A passive acoustic detection system for detecting noise radiating devices in a noise environment comprising: a first acoustic transducer responsive to acoustic signals in its environment; a source of acoustic signals producing signals representative of noise in the environment of said first transducer; a first octave-band frequency filter connected to said first transducer for permitting passage of only one band of frequencies; a second octave-band frequency filter connected to said source of acoustic signals for permitting passage of only one band of frequencies; a first automatic level control circuit responsive to the output signal from said first band filter to provide a constant root mean square level for the output signal from said first band filter; a second automatic level control circuit responsive to the output signal from said second band filter to provide a constant root mean square level for the output signal from said second band filter; a first pulse-forming clamp circuit, having a selectably variable threshold level, responsive to the output of said first level control circuit for providing a pulse whenever said threshold level is exceeded; a first means responsive to the output of said first pulse-forming clamp circuit to provide a constant amplitude pulse signal every time said first pulse-forming circuit generates a pulse; a second pulse-forming clamp circuit, having a selectable variable threshold level, responsive to the output of said second level control circuit for providing a pulse whenever said threshold level is exceeded; a second means responsive to the output of said second pulse-forming clamp circuit to provide a constant amplitude pulse signal every time said second pulse-forming circuit generates a pulse; a ratio detector responsive to the output of said first and second means for measuring the ratio of the pulses from said first means to the pulses from said second means; whereby a presence is detected if the ratio of pulses from said first means to said second means equals or exceeds a predetermined amount.
Claim 2
Dependent Claim
324 words
A passive acoustic detection system for detecting noise radiating devices in a noise environment comprising: a first acoustic transducer responsive to acoustic signals in its environment; a source of acoustic signals producing signals representative of noise in the environment of said first transducer; a first octave-band frequency filter connected to said first transducer for permitting passage of only one band of frequencies; a second octave-band frequency filter connected to said source of acoustic signals for permitting passage of only one band of frequencies; a first automatic level control circuit responsive to the output signal from said first band filter to provide a constant root mean square level for the output signal from said first band filter; a second automatic level control circuit responsive to the output signal from said second band filter to provide a constant root mean square level for the output signal from said second band filter; a first pulse-forming clamp circuit, having a selectably variable threshold level, responsive to the output of said first level control circuit for providing a pulse whenever said threshold level is exceeded; a first means responsive to the output of said first pulse-forming clamp circuit to provide a constant amplitude pulse signal every time said first pulse-forming circuit generates a pulse; a second pulse-forming clamp circuit, having a selectable variable threshold level, responsive to the output of said second level control circuit for providing a pulse whenever said threshold level is exceeded; a second means responsive to the output of said second pulse-forming clamp circuit to provide a constant amplitude pulse signal every time said second pulse-forming circuit generates a pulse; a ratio detector responsive to the output of said first and second means for measuring the ratio of the pulses from said first means to the pulses from said second means; whereby a presence is detected if the ratio of pulses from said first means to said second means equals or exceeds a predetermined amount.
Claim 3
Dependent Claim
14 words
The detection system of claim 1 wherein said first acoustic transducer comprises a hydrophone.
Claim 4
Dependent Claim
34 words
The detection system of claim 1 wherein said first and second octave-band frequency filters selectively provide a plurality of optimized frequency pass bands as determined by the DUCA characteristics of the radiated noise signal.
Claim 5
Dependent Claim
14 words
The detection system of claim 3 wherein said first acoustic transducer comprises a hydrophone.
Claim 6
Dependent Claim
24 words
The detection system of claim 1 wherein said source of acoustic signals comprises a second acoustic transducer responsive to acoustic signals in its environment.
Claim 7
Dependent Claim
25 words
The detection system of claim 5 wherein said first acoustic transducer comprises a directional acoustic transducer and said second acoustic transducer comprises an omnidirectional transducer.
Claim 8
Dependent Claim
40 words
The detection system of claim 6 wherein said first and second automatic level control circuits are disposed so as to be switchably inserted and removed from in between the respective said octave-band frequency filters and said pulse forming clamp circuits.
Claim 9
Dependent Claim
23 words
The detection system of claim 7 wherein said directional acoustic transducer comprises a directional hydrophone and said omnidirectional transducer comprises an omnidirectional hydrophone.
Claim 10
Dependent Claim
22 words
The detection system of claim 7 wherein said first and second octave-band frequency filters selectively provide a plurality of frequency pass bands.
Claim 11
Dependent Claim
23 words
The detection system of claim 9 wherein said directional acoustic transducer comprises a directional hydrophone and said omnidirectional transducer comprises an omnidirectional hydrophone.
Claim 12
Independent Claim
214 words
A method for detecting the presence of noise generating devices in a noise environment comprising the steps of: monitoring the environment for acoustic signals by a transducer having directional sensitivity and a transducer having omnidirectional sensitivity; transducing the directionally monitored acoustic signals into electrical signals in a first channel; transducing the omnidirectionally monitored acoustic signals into electrical signals in a second channel; filtering the electrical signals in the first channel by a first adjustable band pass filter; filtering the electrical signals in the second channel by a second adjustable band pass filter; generating a pulse signal every time the amplitude of the transduced electrical signal in the first channel exceeds a predetermined threshold value; generating a pulse every time the amplitude of the transduced electrical signal in the second channel exceeds the same predetermined threshold value; counting the number of times a pulse signal is generated in the first channel in a predetermined time period; counting the number of times a pulse signal is generated in the second channel in the same predetermined time period. comparing the count in the first channel with the count in the second channel; indicating detection of a noise generation device if the count in the first channel exceeds the count in the second channel by a predetermined ratio.
Claim 13
Independent Claim
214 words
A method for detecting the presence of noise generating devices in a noise environment comprising the steps of: monitoring the environment for acoustic signals by a transducer having directional sensitivity and a transducer having omnidirectional sensitivity; transducing the directionally monitored acoustic signals into electrical signals in a first channel; transducing the omnidirectionally monitored acoustic signals into electrical signals in a second channel; filtering the electrical signals in the first channel by a first adjustable band pass filter; filtering the electrical signals in the second channel by a second adjustable band pass filter; generating a pulse signal every time the amplitude of the transduced electrical signal in the first channel exceeds a predetermined threshold value; generating a pulse every time the amplitude of the transduced electrical signal in the second channel exceeds the same predetermined threshold value; counting the number of times a pulse signal is generated in the first channel in a predetermined time period; counting the number of times a pulse signal is generated in the second channel in the same predetermined time period. comparing the count in the first channel with the count in the second channel; indicating detection of a noise generation device if the count in the first channel exceeds the count in the second channel by a predetermined ratio.
Claim 14
Dependent Claim
67 words
The method of claim 11 wherein the filtered electrical signals in the first channel are kept at a constant predetermined root mean square level before the step of generating a pulse signal in the first channel; and the filtered electrical signals in the second channel are kept at a constant predetermined root mean square level before the step of generating a pulse signal in the second channel.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-04-03 | 1981-10-03 | 1982-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-03 | 1985-10-03 | 1986-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-03 | 1989-10-03 | 1990-04-04 | $7700.00 | Window Closed / Lapsed |