Impulse Response Measurer: Amplitude of recorded signal is almost half compared to recording in audacity
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Mehmet Cibir
le 12 Fév 2022
Commenté : Jimmy Lapierre
le 16 Fév 2022
Hi,
i have recently been working with the impulse response of a room and wanted to determine it myself without the impulseresponsemeasurer, using the results of the tool as a guide for my own attempts.
I have now noticed that the recorded values from the irdata table are about half the size of the recorded values from audacity.
I use the saved signal to be sent from the irdata table and play it back in audacity, while simultaneously recording in audacity. Playback volume is the same in both cases, recording volume is also the same.
I can't explain now how these differences come about, since the same hardware is used.
In the picture you can see that the recorded signals are the same in their characteristics - only the values for the amplitude do not match. I am not sure now if I get wrong values for the impulse response in the impulseresponsemeasurer, because the ratio of the signal to be played and the recorded signal do not fit...
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/892725/image.png)
Is this how it should be?
Have I overlooked something in the documentation?
Am I on the wrong track? Are the values in audacity wrong?
Is there a hidden option/value for the recording volume in matlab which affect the recorded values?
If someone could make similar observations or give me a tip how these deviations come about I would be grateful.
Greetings,
Mehmet
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Jimmy Lapierre
le 14 Fév 2022
Playback level in the impulseResponseMeasurer is controlled by the "Excitation Level (dBFS)" setting in the toolbar. Does setting that to 0 dBFS get you more in line with what you expect?
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Image Analyst
le 12 Fév 2022
I had the opposite situation. In audacity, it recorded a signal and said it was going from -0.5 to +0.5 with lots of clipping at -0.5 and +0.5 (which may have been caused by the dictation recorder I had used to record the conversation). Then I told Audacity to export it to .mp3 format and read it into MATLAB and now the values go from -0.7 to +0.7. The waveform doesn't have flat tops like in Audacity so I think that those might have been changed upon conversion to MP3 format, which changes the signal due to lossy compression.
What format did you export the signal to from Audacity?
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