Abstract
In the Lord Corporation 423 cubic meter reverberation room, a microcomputer‐controlled instrumentation system has been implemented to measure sound absorption and to determine sound power. The kernel of the system is a Cromemco Z‐2D microcomputer (Z‐80 microprocessor) with dual disk drives and a seven‐channel A/D converter. Amplified and filtered microphone signals are taken directly from the parallel outputs of a General Radio 1/3‐octave multifilter and fed to an in‐house built interface. The interface consists of 28 parallel true rms detectors (Analog Devices ♯536) and seven 4X‐multiplexers (RCA ♯CD4151). An important feature of the AD536 converter is the availability of a decibel output with a useful dynamic range of 60 dB. Separate averaging time constants can be selected for each channel. The overall system is quite inexpensive yet extremely flexible and powerful; both Fortran IV and 16K Extended Basic software are available. A description of the system and its performance are given.
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