Portable Recorder for Acoustical Measurements
George W. Kamperman · The Journal of the Acoustical Society of America · 1956
This paper describes the modifications performed on a commercial audio magnetic-tape recorder to convert it into a moderate-cost, portable, field instrument for use in making acoustical measurements such as reverberation time, noise spectra, etc. An Ampex Model 600 recorder was chosen because of inherent features that make it readily adaptable for this purpose. The principal modifications include a precision step attenuator in the recording amplifier, an increase in tape speed from 712 to 15 in./sec, a peak signal overload indicator, a pre-emphasis filter selector, and a second recording channel.