Extech sl355 sound level measuring apparatus noise measuring apparatus extech sl355 the extech sl355 personal noise dosimeter datalogger stores up to 20 dosimeter surveys which includes the start stop time dose dose projected for an 8 hour period and peak level when used in the dosimeter mode it can log up to 12 000 readings when used as a sound level meter with sampling times between 1sec and 1hr with the supplied windows reg xp vista 7 compatible software connected via the usb inte