| 摘要 |
A cumulative sound exposure instrument has an alarm indicator responsive to a selected maximum instantaneous loudness level and has a second indicator which is responsive to a selected value of accumulated exposure. A register provides a continuous reading of the amount of exposure. The instrument integrates a function over time to give a reading that accumulates faster for higher loudness levels. The elements that accomplish these functions include a sound pickup system which applies a signal to a frequency compensating shaping system for shaping the signal output in accordance with an ear's response. An amplitude responsive shaping network receives the signal and applies an output to a pulser in accordance with the function which will be integrated. The pulser output is proportional to the voltage of the input and drives a counter to accumulate an exposure reading. Minimum and maximum threshold detectors control the pulser output so that the counter is driven only when the loudness level lies between two preset limits.
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