I am preparing a DIY home recording studio. I did four experiments a new Samson C01U plugged into a Mac computer and recording into Audacity. I recorded background noise in one room without furniture and with a lot of echo; in the adjacent room with furniture and 5 foam mattress; in the closet of that second room; and in that room with more foam padding around the microphone.
I analyzed the noise level with
ffmpeg -i recording -af loudnorm=I=-24:TP=-9:LRA=7:print_format=summary -f null -
The noise in the closet is:
mean_volume: -80.8 dB max_volume: -67.4 dB
The noise in the three other locations is the same at the decibel decimal level:
mean_volume: -83.3 dB max_volume: -70.3 dB
To make sense of these numbers, I hypothesize that the main source of noise in the three room settings is the self-noise from the microphone and the noise from the Mac computer, and that this noise is reverberated in the small closet and increases the noise level by 3 dBs.
The Samson C01U data sheet does not mention self-noise. An Amazon.com page for Samson C01 mentions "Self Noise: 23 dB", so I can't immediately judge this number compared to the average volume of -83.3 dB. The microphone has a hypercardiod pattern and the computer is to the side.
Is this true? Or should I pad the room with more foam to decrease the level of background noise?
Update: On a different day, I did the same test and got more variation in the results: mean volume between -67.2 and -69.2 dB and max volume between -52.7 and -56.2 dB. Having the laptop inside or outside the room made only a 0.2 dB difference in the mean volume. So maybe the ambience is the main source of background noise, especially as the recordings are half a kilometer from the beach and the wind and waves are strong today.