USB problems

If you use a USB microphone such as the MiniDSP Umik, you may find a problem with your measured impulse response : the impulse itself is not clean and shows many peaks together instead of just one. This may come from USB problems : gliches or short drop-outs while recording gives such problem. The clock drift itself, coming from a mismatch between player clock and recording clock is compensated by resampling the log sine sweeps thanks to dual chirps at start and end of the audio sequence.

Glitches or drop-outs may be avoided by checking and optimising following parameters :

  • remember that the max length of a non-damaged cable is about 3m for USB class 1 (so try with another certified cable)
  • in windows configuration/system/advanced parameters : adjust for best performances and activate “background services”
  • USB sharing : change USB port and try tu use a port not shared by other components,
  • in BIOS, try to modify PCI bridge latency timer (PCIe don’t have latency timers)
  • in BIOS, disable CPU throttling
  • disable unused sound devices
  • disabled all energy saving options and set power plan to max efficiency
  • set highest priorities to the recording process
  • deactivate temporarelly your antivirus
  • some usefull links :

Optimise Audacity and computer

Optimising-your-PC-for-Audio-on-Windows-10

PC-Optimization-Guide-for-Windows-8

Troubleshoot-USB-dropouts-audio-glitches-Windows

Troubleshoot-USB-dropouts-audio-glitches-Mac

Test USB latency

AES paper 8169 : Impulse response measurements in the presence of clock drift