noiseLAB supports up to 8 simultaneous parallel acoustic channels.
The following is a guide to configuring this most economically:
- For a noise floor of about 30 dB(A) use one National Instruments USB 9234 with four active microphone channels.
- For a noise floor of about 17 dB(A) use a microphone preamp with 20 dB gain and two active channels. This gain setting requires additional power from the USB 9234, therefore only two channels can be used and each channel must be coupled in parallel to an unused inputs to get sufficient powering.
4-8 channels (partial synchronization)
- User two National Instruments 9234.
- With a noise floor or 30 dB(A) you can use up to 8 channels.
- With a noise floor of 17 dB(A) you can use to up 4 channels as described above.
- The two channels in each 9234 are synchronized, but the two 9234 devices are not synchronized between each other. Hence precise time relationships cannot be determined, since the internal clocks in the 9234s may drift several seconds per day.
4-8 channels (full synchronization)
- Solution 1: Use two National Instruments 9234 in a CompactDAQ Chassis cDAQ 9174 which synchronizes the two modules. The powering constraints described above are the same.
- Solution 2: Use the National Instruments PCI 4474 (four channels) or PCI 4472 (8 channels) in a PC with a full size PCI slot. (Note: PCIe slots cannot be used). These cards provide 4 or 8 fully synchronized channels, and 8 dB greater dynamic range than the NI 9234. In addition, each channel provides sufficient powering to drive preamps with 20 dB gain. Finally, twice as high sampling frequencies as the 9234 are supported.
- Two USB digitizers connected to noiseLAB must be identical and configured with the same sampling frequency.
- The 9233 is NOT recommended since it cannot turn off its IEPE powering, and also has “end of life” status at National Instruments.