| 摘要 |
A portable, fully automatic instrument for at any given time determining precisely a person's cumulative noise exposure as a percentage of permissible noise exposure is disclosed. The instrument includes a microphone for sensing sound levels, a sound level measuring circuit, an A weighting circuit, a rectifying circuit, a variable-gain ratio amplifier, a noise threshold level circuit for removing from consideration the noise levels below a predetermined threshold level, a converter output circuit, and a readout device for indicating the cumulative percentage of allowable noise exposure that has been experienced. The instrument converts incident sound level pressures in excess of the predetermined threshold level for the time periods of occurrence of the various sound levels into a representation indicative of a cumulative percentage of permissible noise exposure. A method for sensing sound levels above a predetermined threshold, providing a continuous summation of the sound levels for their respective time periods of occurrence, and conversion of the resultant summation to a cumulative percentage of permissible noise exposure is also disclosed.
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