Included in every Apex 3-Series Wireless Headset, the Sonetics Personal Sound Dosimeter (PSD), is the first line of defense for your hearing protection plan, alerting you to potentially hazardous noise levels. The PSD measures sound pressure levels using microphones inside the headset’s ear domes. The PSD records sound exposure data for up to 24 hours, or until the PSD is reset. The PSD uses the data it collects about your noise exposure to begin lowering the maximum sound level of your headset’s speakers until you reach the 85dB threshold specified by OSHA standard 1901.95(c)(1). To put that in context, normal conversation is about 60dB. When the PSD reaches 60% of total allowable noise exposure, it begins to lower the maximum decibel level of the headset’s ear dome speakers in steps, from 95dB down to 85dB after the PSD has recorded 90% of your maximum allowable noise exposure. The PSD reports total noise exposure when you power down the headset. A voice prompt announces “Dosimeter” and a number from 0 to 100. The number is a percentage of your total time-weighted noise exposure over an eight-hour period.