Hello
I am dabbling in soundproof construction (not professional). I built myself a workshop and I want to test its acoustic insulation performance, and the difference before and after double glazing (DIY acrylic).
So anyway, to do this test I used Audacity to generate a sequence of pure tones at the standard OITC (like STC) frequencies, ie
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
- each 0.7 seconds long.
To define a baseline in open air I played this through a bluetooth speaker and recorded it on a Rode VideoMic at a distance of 2m.
Then I selected each time period and measured the RMS volume:
| Frequency | Open air inside |
|---|---|
| 80 | -24.6 |
| 100 | -16.7 |
| 125 | -13.1 |
| 160 | -12.1 |
| 200 | -0.8 |
| 250 | -10.2 |
| 315 | -3.2 |
| 400 | 7 |
| 500 | -4.4 |
| 630 | 12.1 |
| 800 | 7 |
| 1000 | 10 |
| 1250 | 0.8 |
| 1600 | -8.9 |
| 2000 | -5.7 |
| 2500 | 8 |
| 3150 | 2.6 |
| 4000 | 7.4 |
I also measured the background sound level at about -47 dB. This was inside a quiet room.
Fine. The problem is that when I record through a wall from outside, the sound is faint, and it gets mixed up with other noise.
You can see the signal of interest on the spectrogram. What I would like to do is to isolate or measure the volume of that specific tone in the recording, without the other noise.
This seems like it should be possible, but I couldn’t figure out how. I’m new to audio processing. A windowed minimum filter across the spectrogram would do it?
