Environmental noise monitoring
First Claim
1. An environmental noise monitoring system, comprising:
- three or more sound level transducers arranged apart from each other in an environment containing one or more noise sources, each transducer is arranged to pick up sounds arriving from any direction and to transduce the sounds into electrical signals;
sound level and direction measuring equipment, including;
signal samplers connected to respective transducers to receive electrical signals representing environmental sounds and to sample the electrical signals, whereby pairs of sampled signals are formed with each pair representing sampled signals from two of the three or more sound level transducers; and
a computer processor to;
perform cross correlation calculations to generate a cross correlation function for each pair of sampled signals,identify local maxima in each cross correlation function;
determine two possible sound arrival directions with respect to a fixed directional system for each identified local maximum;
determine sets of possible sound arrival directions for each pair of sound level transducers in each cross-correlation function;
compare the determined sets of possible sound arrival directions to find matches whereby the same sound arrival direction appears in determined sets of each cross-correlation function to within a predetermined tolerance and thereby indicate the direction of the one or more noise sources; and
determine, for each match found, the sound pressure level of an associated noise source based on values of the cross-correlation functions at the associated local maxima.
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Accused Products
Abstract
This invention concerns environmental noise monitoring, and more particularly a system and method for environmental noise monitoring. The environmental noise monitoring system comprises three or more sound level transducers arranged apart from each other in an environment containing one or more noise sources. Each transducer is arranged to pick up sounds arriving from all directions and to transduce the sounds into electrical signals. The sound level and direction measuring equipment includes signal samplers connected to respective transducers to receive electrical signals representing environmental sounds and to sample the electrical signals. A computer processor is further provided to perform cross correlation calculations to generate a cross correlation function for each pair of sampled signals. The processor identifies local maxima in the cross correlation functions, estimates the angle of arrival of the sound associated with a local maximum and the sound pressure level associated with the maximum, and uses the estimates of the angles from all cross correlation functions to identify a source of noise in a particular direction and the level of noise from that source, and then identifies additional sources of noise in different directions and the levels of noise from those sources. Noise levels from sources in particular directions may be accumulated, displayed and saved for reference.
32 Citations
23 Claims
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1. An environmental noise monitoring system, comprising:
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three or more sound level transducers arranged apart from each other in an environment containing one or more noise sources, each transducer is arranged to pick up sounds arriving from any direction and to transduce the sounds into electrical signals; sound level and direction measuring equipment, including;
signal samplers connected to respective transducers to receive electrical signals representing environmental sounds and to sample the electrical signals, whereby pairs of sampled signals are formed with each pair representing sampled signals from two of the three or more sound level transducers; anda computer processor to; perform cross correlation calculations to generate a cross correlation function for each pair of sampled signals, identify local maxima in each cross correlation function; determine two possible sound arrival directions with respect to a fixed directional system for each identified local maximum; determine sets of possible sound arrival directions for each pair of sound level transducers in each cross-correlation function; compare the determined sets of possible sound arrival directions to find matches whereby the same sound arrival direction appears in determined sets of each cross-correlation function to within a predetermined tolerance and thereby indicate the direction of the one or more noise sources; and determine, for each match found, the sound pressure level of an associated noise source based on values of the cross-correlation functions at the associated local maxima. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of monitoring environmental noise, the method comprising the steps of:
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using each of three or more sound level transducers arranged apart from each other in an environment containing one or more noise sources, to pick up sounds arriving from any direction; transducing the sounds into electrical signals; sampling the electrical signals; forming pairs of sampled signals, each pair representing sampled signals from two of the three or more sound level transducers; performing cross correlation calculations to generate a cross correlation function for each pair of sampled signals; identifying local maxima in each cross correlation function; determining two possible sound arrival directions with respect to a fixed directional system for each identified local maximum; determining sets of possible sound arrival directions for each pair of sound level transducers in each cross-correlation function; comparing the determined sets of possible sound arrival directions to find matches whereby the same sound arrival direction appears in determined sets of each cross-correlation function to within a predetermined tolerance thereby indicating the direction of the one or more noise sources; and determining, for each match found, the sound pressure level of an associated noise source based on values of the cross-correlation functions at the associated local maxima. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. Sound level and direction measuring equipment, the equipment comprising:
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signal samplers connected to respective sound level transducers to receive electrical signals representing environmental sounds and to sample the electrical signals, whereby pairs of sampled signals are formed with each pair representing sampled signals from two of three or more sound level transducers; and a computer processor to; perform cross correlation calculations to generate a cross correlation function for each pair of sampled signals; identify local maxima in each cross correlation function; determine two possible sound arrival directions with respect to a fixed directional system for each identified local maximum; determine sets of possible sound arrival directions for each pair of sound level transducers in each cross-correlation function; compare the determined sets of possible sound arrival directions to find matches whereby the same sound arrival direction appears in determined sets of each cross-correlation function to within a predetermined tolerance and thereby indicate the direction of the one or more noise source; and determine, for each match found, the sound pressure level of an associated noise source based on values of the cross-correlation functions at the associated local maxima. - View Dependent Claims (21, 22, 23)
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Specification