Acoustic monitor
First Claim
1. An electronic monitor that monitors sound produced by a sound source and that detects abnormalities and operating conditions thereof, comprising:
- a microphone located in proximity to the sound source that detects sound emanating from the sound source and generates an analog electrical signal representative of the sound within an audible frequency range over a plurality of octaves;
an analog signal conditioning circuit coupled to the microphone that conditions the analog electrical signal from the microphone and converts it to a differential analog signal;
an analog-to-digital converter that samples the differential analog signal at regular intervals and that converts it to a stream of digital samples;
a digital filter coupled to the analog-to-digital converter that processes the stream of digital samples from the analog-to-digital converter continuously and in real time using a plurality of fractional octave digital bandpass filters to obtain a real-time acoustic power spectrum of the sound, the real-time acoustic power spectrum of the sound comprising a plurality of time-average acoustic power outputs from the plurality of fractional octave digital bandpass filters;
the monitor having a learning mode and an operating mode such that an acoustic signature copy of the real-time acoustic power spectrum of the sound is produced in the learning mode and such that test copies of the real-time acoustic power spectrum of the sound are continuously generated during the operating mode;
a memory that receives and stores the acoustic signature copy of the real-time acoustic power spectrum of the sound when the monitor is in the learning mode; and
a comparitor that compares the acoustic signature copy of the real-time acoustic power spectrum of the sound with the test copies of the real-time acoustic power spectrum of the sound, the comparison further comprising a comparison of each of the plurality of time-average acoustic power outputs from the plurality of fractional octave digital bandpass filters, and the monitor generating a warning signal when the comparison indicates that any of the test copies are not within an acceptable range of the signature copy.
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Accused Products
Abstract
An electronic monitor is disclosed which continuously monitors the sound emanating from rotating machinery, non-rotating equipment, or any other sound-producing process or environment, as a means of detecting abnormalities and thus determining the operating condition thereof. The monitor continuously computes the power spectrum of the monitored sound and has two modes of operation: learn and operate. The monitor is placed in the learn mode during a time when the machine or process to be monitored is known to be operating normally. During the learn mode, the maximum and minimum acoustic power output from each of a plurality of digital bandpass filters is continuously maintained and updated in data memory as the acoustic signature of the machine or process being monitored. During the operate mode, the monitor continuously compares the real-time filter outputs with the acoustic signature stored during the learn mode and activates a panel lamp and relay if the output of any of the bandpass filters deviates from the upper or lower decibel limits of the acoustic signature by more than the setting of the corresponding front panel sensitivity selector switch. In its preferred form, the monitor is capable of storing and utilizing up to five acoustic signatures, selectable by either an operator or a host controller, with the signatures being stored in non-volatile data memory. Two alarm levels are provided by the monitor: warning, to indicate a developing fault, and danger, to indicate a situation requiring immediate corrective action.
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Citations
15 Claims
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1. An electronic monitor that monitors sound produced by a sound source and that detects abnormalities and operating conditions thereof, comprising:
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a microphone located in proximity to the sound source that detects sound emanating from the sound source and generates an analog electrical signal representative of the sound within an audible frequency range over a plurality of octaves;
an analog signal conditioning circuit coupled to the microphone that conditions the analog electrical signal from the microphone and converts it to a differential analog signal;
an analog-to-digital converter that samples the differential analog signal at regular intervals and that converts it to a stream of digital samples;
a digital filter coupled to the analog-to-digital converter that processes the stream of digital samples from the analog-to-digital converter continuously and in real time using a plurality of fractional octave digital bandpass filters to obtain a real-time acoustic power spectrum of the sound, the real-time acoustic power spectrum of the sound comprising a plurality of time-average acoustic power outputs from the plurality of fractional octave digital bandpass filters;
the monitor having a learning mode and an operating mode such that an acoustic signature copy of the real-time acoustic power spectrum of the sound is produced in the learning mode and such that test copies of the real-time acoustic power spectrum of the sound are continuously generated during the operating mode;
a memory that receives and stores the acoustic signature copy of the real-time acoustic power spectrum of the sound when the monitor is in the learning mode; and
a comparitor that compares the acoustic signature copy of the real-time acoustic power spectrum of the sound with the test copies of the real-time acoustic power spectrum of the sound, the comparison further comprising a comparison of each of the plurality of time-average acoustic power outputs from the plurality of fractional octave digital bandpass filters, and the monitor generating a warning signal when the comparison indicates that any of the test copies are not within an acceptable range of the signature copy. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 15)
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- 10. The electronic monitor of claim wherein the warning signal comprises two alarm signal levels, a first alarm signal level indicating a developing problem and a second alarm signal level indicating a situation requiring immediate corrective action.
Specification