The testo 815 is the ideal instrument for the evaluation of sound level in everyday work. The instrument can be used for monitoring measurements in the areas of air conditioning or heating, on combustion plants or at workplaces, however machine or discotheque noise can also be evaluated quickly and precisely. Using the Fast/slow button, the measurement time can be set from 1 s to 125 ms, in order to better evalaute the noise source. The frequency analysis can also be switched from characterisitc curve A to C. The characteristic curve A corresponds to the sound pressure perception of the human ear, whereas characteristic curve C can also evaluate the low-frequency components of a sound. With the help of the optional calibrator, the measuring instrument can be recalibrated directly on site with the screwdriver provided. The wind protection cap included in delivery ensures correct measurement results when measuring outdoors, and if required can protect the microphone from dirt and dust.