Method and Apparatus for Acoustic Sensing of Structures

• US 20050193818A1
• Filed: 02/03/2005
• Published: 09/08/2005
• Est. Priority Date: 02/03/2004
• Status: Active Grant

• Current Assignee: University of Denver
• Original Assignee: University of Denver
• Inventors: Cobb, Wesley N.
• Granted Patent: US 7,296,472 B2
• Time in Patent Office: Days
• US Class Current: 73/579
• CPC Class Codes: G01S 15/523 for presence detection burglar, theft or intruder alarms G08B13/00, e.g. G08B13/16
• CPC Class Codes: G01V 1/005 with exploration systems emitting special signals, e.g. frequency swept signals, pulse sequences or slip sweep arrangements

Abstract

A method and system provides for acoustic sensing of structures, including a general shape and/or configuration of the structure and movement within the structure. Acoustic waves are used to characterize structures, including any activity within. As waves from a sound source travel into the structure, they resonate within cavities and connecting tunnels or halls. This acoustic resonance is received at an acoustic receiver. The received signal is analyzed in comparison to the generated signal, and properties of the structure are determined, including the size and shape of the structure, as well as movement of objects within the structure.

Claims

1. An apparatus for sensing characteristics of a structure, comprising:

an acoustic generator operable to generate acoustic waves directed into an entrance of the structure, said acoustic waves generating acoustic resonance within at least a portion of the structure, said acoustic resonance generating resonance acoustic waves;

an acoustic receiver operable to receive said resonance acoustic waves from the entrance of the structure; and

a control system operably interconnected to said acoustic generator and said acoustic receiver and operable to receive a signal from said acoustic receiver corresponding to said resonance acoustic waves and analyze said signal to determine at least a movement of an object within the portion of the structure associated with said acoustic resonance.

2. The apparatus for sensing characteristics of a structure, as claimed in claim 1, wherein said acoustic generator comprises:

a loudspeaker;

a power amplifier operably interconnected with said loudspeaker and operable to drive said loudspeaker to generate said acoustic waves; and

a frequency sweep generator operably interconnected to said power amplifier and operable to deliver a frequency varying signal to said amplifier.

3. The apparatus for sensing characteristics of a structure, as claimed in claim 2, wherein said acoustic generator further comprises:

a sweep trigger operably interconnected to said frequency sweep generator and operable to control said frequency sweep generator to deliver said frequency varying signal, wherein said sweep trigger controls a rate at which the frequency of said frequency varying signal is adjusted.

4. The apparatus for sensing characteristics of a structure, as claimed in claim 2, wherein said acoustic generator further comprises:

a sweep trigger operably interconnected to said frequency sweep generator and operable to control said frequency sweep generator to deliver said frequency varying signal, wherein said sweep trigger controls a range of frequencies at which the frequency of said frequency varying signal is adjusted.

5. The apparatus for sensing characteristics of a structure, as claimed in claim 4, wherein said range of frequencies is selected based on expected characteristics of the structure.

6. The apparatus for sensing characteristics of a structure, as claimed in claim 1, wherein said acoustic receiver comprises:

a microphone; and

a preamplifier operably interconnected to said microphone.

7. The apparatus for sensing characteristics of a structure, as claimed in claim 6, wherein said acoustic receiver further comprises:

a spectrum analyzer operably interconnected to said preamilifier and operable to generate a spectra of signals received at said microphone; and

a structural characteristics estimator operably interconnected to said spectrum analyzer and operable to receive said spectra of signals from said spectrum analyzer and analyze said spectra to generate an estimation of the structural characteristics of the portion of the structure generating said resonance acoustic waves.

8. An apparatus for sensing characteristics of a structure, comprising:

an acoustic generator operable to generate acoustic waves directed into an entrance of the structure, said acoustic waves generating acoustic resonance within at least a portion of the structure, said acoustic resonance generating resonance acoustic waves;

an acoustic receiver operable to receive said resonance acoustic waves from the entrance of the structure; and

a control system operably interconnected to said acoustic generator and said acoustic receiver and operable to receive a signal from said acoustic receiver corresponding to said resonance acoustic waves and analyze said signal to determine at least one of a size and location of connecting chambers and/or connecting segments within the portion of the structure associated with said acoustic resonance.

9. The apparatus for sensing characteristics of a structure, as claimed in claim 8, wherein said control system comprises a structural characteristics estimator operable to determine resonance peaks of said resonance acoustic waves and compare said resonance peaks to predetermined resonance peaks of known structural characteristics and determine said structural characteristics based on said comparison.

10. The apparatus for sensing characteristics of a structure, as claimed in claim 9, wherein said structural characteristics estimator is operable to perform a least squares fit between said resonance peaks and said predetermined resonance peaks and generate an estimate of said structural characteristics.

11. The apparatus for sensing characteristics of a structure, as claimed in claim 8, wherein said acoustic receiver comprises:

a microphone;

a preamplifier operably interconnected to said microphone;

a spectrum analyzer operably interconnected to said preamilifier and operable to generate a spectra of signals received at said microphone; and

a motion and direction detector operably interconnected with said spectrum analyzer and operable to receive a plurality of spectra from said spectrum analyzer and generate an estimation of motion of objects within the portion of the structure generating the resonance acoustic waves.

12. The apparatus for sensing characteristics of a structure, as claimed in claim 11, wherein said motion and direction detector is operable to compare successive spectra of said plurality of spectra and estimate movement based on a difference in resonance peaks between the successive spectra.

13. A method of sensing activity within a structure, comprising:

sending acoustic waves into an interior portion of the structure;

measuring acoustic waves returning as reflections from walls and objects within the interior portion of the structure;

calculating a frequency spectrum of the acoustic waves returned from the structure interior; and

deriving from resonance peaks of said frequency spectrum a measure of the activity within the structure.

14. The method of claim 13, wherein said deriving step comprises:

receiving at least two successive frequency spectra; and

comparing successive spectra of said at least two successive frequency spectra; and

estimating activity based on a difference in resonance peaks between the successive spectra.

15. The method of claim 13, further comprising:

estimating structural characteristics of the structure based on said frequency spectrum.

16. The method of claim 15, wherein said structural characteristics comprise at least one of a size and location of chambers and/or connecting segments within the interior space.

17. A method of determining characteristics of a structure, comprising:

sending acoustic waves into an interior space of the structure;

measuring acoustic waves returning as reflections from walls and objects within the interior space;

calculating a frequency spectrum of the acoustic waves returned from the interior space; and

deriving from resonance peaks of said spectrum an estimate of at least one of a size and location of

chambers and/or connecting segments within the interior space.

18. The method of claim 17, wherein said deriving step comprises:

determining resonance peaks of said spectrum;

comparing said resonance peaks to predetermined resonance peaks associated with structures having known structural characteristics; and

determining said structural characteristics based on said comparison.

19. The method of claim 18, wherein said determining said structural characteristics comprises:

performing a least squares fit between said resonance peaks and said predetermined resonance peaks and generating an estimate of said structural characteristics.

20. The method of claim 17, further comprising:

secondly deriving from said frequency spectrum a measure of activity within the interior space.

21. The method of claim 20, wherein said secondly deriving step comprises:

receiving at least two successive frequency spectra; and

comparing successive spectra of said at least two successive frequency spectra; and

estimating activity based on a difference in resonance peaks between the successive spectra.