This assembly comprises a laboratory quality system for the measurement and analysis of sound over the frequency range of 20 c/sec. to 150 kc/sec. Its principal components are: (1) A hydrophone amplifier having the input characteristics of a cathode follower and a balanced line output. The response is uniform within 1 db from 10 c/sec. to 130 kc/sec. (2) A sound level meter provided with both peak and r.m.s. meters with linear db Scales. (3) A separate power supply, resulting in greater portability and allows either battery, 60 cycle or 400 cycle power to be used. (4) A calibration test set. Provision is made for inserting a half-octave filter set for analysis and for simultaneously feeding a magnetic tape recorder and a graphic level recorder.