Hello
I have an audio recording of environmental noise, about 8 sec of the recording. Processed it to reveal the frequency bands carrying the most energy and filter it out.
Used spectrogram in order to see the frequency spread over timeline of the recording, looks like the most is focused in lower band of under 100 Hz thoughout the entire recording. Attached is the spectrogram results.
Then used pwelch to figure the most energetic frequency band, showing peak and about 40 Hz. Used Butterworth order 5 HPF at cutoff of 120 Hz to suppress the low band.
The pwelch of the original recording and the filtered data is attached. Looks like shaved off the low band nicely up to about 120 Hz.
Printed out the sound data before and after the filtration - the difference in the std is obvious.
With all that, when I'm streaming the original and filtered signal to my PC speakers (using either sound() or audioplayer() functions) - it sounds idential to my ears in frequency content and in volume (of course, given the same PC volume).
I'd expect the filtered signal would sound much quieter due to the band carrying most of the energy is filtered out.
What do I miss in my understanding ?
P.S. the original WAV file is also attached just in case
Thanks to all willing to help
