Larson Davis Model 831 Class 1 Sound Level Meter. This versatile instrument, with high definition display, performs the functions of several instruments. It puts the combined features of a precision Class 1 sound level meter, environmental noise analyzer, personal noise dosimeter, and a real-time frequency analyzer in the palm of your hand. The Larson Davis Model 831 is a fifth generation Larson Davis sound level meter, designed for simple single handed operation, yet is fully featured, smart and versatile with an ever expanding firmware platform. The design of the Model 831 was based on countless inputs from our customers. It expands upon the Larson Davis tradition of delivering value, innovation and function in a rugged single-handed expandable package and is backed by our 2-year Factory Warranty, 24-hour application support and accredited factory service/calibration.