No audio tape, recording using charting software. The test I use the LASER interferometer in involves dropping a rod and measuring the bounce. The unit chosen was the model ILD 1700-20 from my link. That unit has a start of measurement range of 40mm and an end of measurement range of 60mm with 50 mm being the point of reference. The unit provides 0 volt out at 40mm and 10 volts out at 60mm. Therefore from start to stop I have 20mm and 0 to 10 volts over that 20mm.
That analog output is fed to my software. For this particular test I use
one of these units which gives me 14-bit, 150kHz waveform recording capability. More than adequate speed and resolution for this particular test. Within the software on the chart the 0 to 10 volts is scaled for inches. Anyway, no audio. It would just be a rattling noise followed by a bang then a softer bang.
Ron