Acoustic building infiltration measurement system
Systems and methods of detecting and identifying a leak from a container or building. Acoustic pressure and velocity are measured. Acoustic properties are acquired from the measured values. The acoustic properties are converted to infiltration/leakage information. Nearfield Acoustic Holography (NAH) may be one method to detect the leakages from a container by locating the noise sources.
1. A method of detecting leakage comprising:
emitting sound at a frequency and having a wavelength from an electroacoustic transducer positioned within a structure;
measuring, with a microphone positioned internal to the structure, an internal pressure of the emitted sound within the structure;
positioning a holographic array of microphones external to the structure, the array of microphones positioned, relative to the structure, within half of the wavelength of the emitted sound;
measuring, by nearfield acoustic holography with the array of microphones, external pressure and external velocity of the sound at discrete points on the exterior of the structure;
determining at each of the points an interior-to-exterior acoustic transfer impedance; and
identifying, based upon the determined acoustic transfer impedance, the size and location of a leak in the structure.
2. The method of claim 1 , wherein detecting sound comprises detecting sound by nearfield acoustic holography.
3. The method of claim 2 , wherein detecting sound by nearfield acoustic holography comprises positioning a holographic array comprising a plurality of microphones positioned external to the structure.
4. The method of claim 3 wherein determining the leak comprises applying a nearfield acoustic holography algorithm selected from the group consisting of Fourier transform (FFT) based NAH, Boundary element method (BEM) based NAH, and Equivalent source model (ESM) based NAH.
5. The method of claim 1 , wherein detecting sound comprises detecting sound by a sound intensity probe positioned external to the structure.
6. The method of claim 1 , wherein external pressure is measured by acoustic beamforming.
7. The method of claim 1 , further comprising determining an acoustic transfer impedance of the leak.
8. The method of claim 1 , wherein determining the leak in the structure comprises determining at least one acoustic property based upon the measured internal pressure, external pressure, and velocity.
9. The method of claim 1 , comprising determining a plurality of leaks.
10. The method of claim 9 , further comprising determining the leakage for a section of the structure by adding the determined plurality of leaks corresponding to the section.
11. The method of claim 1 , wherein determining a leak comprises determining the ratio of pressure to velocity for a plurality of sections.
12. The method of claim 1 , wherein the emitted sound is within the range of 100 Hz to 5 kHz and at least 60 dB.
13. A system for detecting leakage of a structure, comprising:
an electroacoustic transducer positioned inside the structure and configured to emit an acoustic wave having a phase, frequency and amplitude;
an interior transducer located inside the structure and in communication with a computer to provide the phase, frequency, and amplitude of the emitted acoustic wave; and
an external acoustic transducer system configured to detect acoustic pressure and acoustic velocity on the outside of the structure within a distance of half of a wavelength of the emitted acoustic wave.
14. The system of claim 13 , wherein the acoustic transducer system comprises an acoustic holography microphone array configured to receive the acoustic waves on the outside of the structure and in communication with the computer.
15. The system of claim 14 , wherein the acoustic holography array comprises an array of pressure transducers.
16. The system of claim 14 , wherein the acoustic holography array is a nearfield acoustic holography array.
17. A computer system for leakage detection comprising:
a loudspeaker configured to emit an acoustic wave having a phase, frequency and amplitude within a structure, an internal microphone positioned within the structure and in communication with a computer to provide the phase, frequency, and amplitude of the emitted acoustic wave;
a microphone array positioned outside of the structure within half of a wavelength of the emitted acoustic wave and configured to receive the acoustic wave, the microphone array in communication with the computer providing acoustic pressure data to the computer;
the computer including a processor and a tangible computer-readable medium operatively connected to the processor and including computer code configured to:
determine leakage from the array acoustic velocity and pressure data associated with each of a plurality of points.
18. The system of claim 17 , wherein the microphone array comprises an array of pressure transducers.
19. The system of claim 17 , wherein the microphone array is a nearfield acoustic holography array.