Peak Level Calibration and wavrec Plugin
Posted: Wed Apr 29, 2020 6:09 am
I have dummy devices connected to the MHA via sound card and want to check, at which level peak clipping kicks in.The peak clipping could be somewhere in the chain, could be from the A/D converters in the soundcard, could be from the microphone in the dummy devices could be from the settings of the MHA. I recorded the signal in the MHA using the wavrec plugin:
If I use the input calibration
amplitudes of my whistle are low. See attached picture lower two lines:
But the calibration is wrong for my set-up and I have to increase the input peak level to:
The recorded wav file now shows an increased amplitude (+15 dB) of my whistle (upper two rows), what is strange because I increased the peak level and the amplitude of the same sound should be lower. It might be, that the wavrec plugin assumes 1 Pa as Peak value, than I understand what happens. Ifso, this infoirmation is missing in the doucmentation.
1) How can I check with MHA, if peak clipping occurs in the input chain?
I recorded now the direct input signal with audacity and can see, that my whistle is not clipping. But this does not check if my settings in the MHA might cause peak clipping. That's already my solution to check this, although I would prefer a solution, where I am able to check this directly in the MHA.
2) Any ideas how I can check with MHA if peak clipping occurs in the input chain?
Last question: If I configure the MHA to a low calibration value (low mic sensitivity) and add e.g. 20 dB of gain so that a sine with 80 dB SPL input level (full scale) have an amplitude above "1". Will this signal be clipped by the MHA or can the MHA internally process signals with amplitudes larger than 1 dB FS? The output calibration might be sufficient to play back the sine with 100 dB SPL:
Thanks,
Dirk
Code: Select all
mha.mhachain.algos=[wavrec...
Code: Select all
calib_in.peaklevel=[120 120]
But the calibration is wrong for my set-up and I have to increase the input peak level to:
Code: Select all
calib_in.peaklevel=[135 135]
1) How can I check with MHA, if peak clipping occurs in the input chain?
I recorded now the direct input signal with audacity and can see, that my whistle is not clipping. But this does not check if my settings in the MHA might cause peak clipping. That's already my solution to check this, although I would prefer a solution, where I am able to check this directly in the MHA.
2) Any ideas how I can check with MHA if peak clipping occurs in the input chain?
Last question: If I configure the MHA to a low calibration value (low mic sensitivity) and add e.g. 20 dB of gain so that a sine with 80 dB SPL input level (full scale) have an amplitude above "1". Will this signal be clipped by the MHA or can the MHA internally process signals with amplitudes larger than 1 dB FS? The output calibration might be sufficient to play back the sine with 100 dB SPL:
Code: Select all
calib_in.peaklevel=[80 80]
calib_out.peaklevel=[120 120]
Dirk