Let $S = X + N$ be the sum of two audio signals $X$ and $N$ which are both stationnary (let's think X is a constant volume 440 Hz sinusoid and N is constant volume noise).
If the sum S has a -20 dB volume and N has a volume of -30 dB, what is the volume of X? (could be RMS or peak volume, it doesn't matter here).
The answer is
20*log10(10^(-20/20)-10^(-30/20)) ~ -23.3
i.e. X has a peak volume of -23.3 dB.
(of course this is not true if X and N have phase-cancellation, but except this case, it works).
Question: what is the name of this computation? i.e. find the volume of X given the volume of N and X + N?
I'm using an application of this for STFT denoising (with a noise template which is N):
- if a FFT bin has -20 dB amplitude (signal S), and the noise has amplitude -30 dB amplitude for the same bin (signal N), what would be the amplitude of the denoised signal X ? Answer: -23.3 dB, thus this FFT bin should be lowered by 3.3 dB.
It works quite well for my noise reduction application (again here X is nearly a constant sinusoid and N constant noise), but I haven't found a name for this simple technique. What would be the name?