Digital acoustic data recording system

Perhaps the weakest link in the acoustic measurement chain has been the analog tape recorder with its limited dynamic range being the most critical parameter. One method for circumventing this problem is to digitize the signal, with a suitable dynamic range system, and record the signal in digital form. An additional requirement imposed on the system is that the reproduced signal should be of a very high audible quality such that recordings obtained might be useful in subjective response to noise experiments. Though many techniques are being implemented to accomplish these ends, e.g., nonbinary bit weighting and multichannel parallel record formats; the approach described here has multiple data channels, binarily weighted and recorded serially on a single tape track. This approach has a linear quantization interval and is not sensitive to tape skew conditions; however, a higher bit rate must be accommodated. A system has been developed which accommodates four channels each having a dc to 20 kHz frequency response and a dynamic range in excess of 75 dB. This information along with time code and voice annotation is recorded on an inexpensive video tape recorder.