Systems and methods for processing information present in a digital audio stream to obtain a measure of gain of an analog-to-digital converter (ADC) preamplifier are disclosed. In one implementation, a method of processing information present in a digitally sampled stream to obtain a measure of ADC preamplifier gain used to digitize the output of a known transducer comprises transforming time-domain digital samples into the frequency domain through use of a discrete Fourier transform (DFT), and using knowledge of the maximum effective frequency associated with the frequency response of the transducer to process frequency-domain data to obtain a measure of the gain of the ADC preamplifier.