Abstract: Acoustical signals of sound and noise levels are analyzed automatically for statistical characteristics of such signals which are required to be measured by recent environmental and health and safety regulations. The signals are applied to an analog to digital converter which tracks rapid changes in signal level and provides a digital output which represents the level in logarithmic (decibel) steps. The digital outputs which exist at successive sampling times provide a history of the sound level characteristics. A memory having a large sample capacity is provided to store these digital level samples. A storage capacity of several million samples is obtained by a random access memory which is addressed by the data representing the sound levels. A separate address is provided for each level (viz., for each of 100 levels differing from each other by 1 dB steps).