Do you have a reference for an algorithm that will do this?
Noise reduction is difficult because any effective noise reduction has to recognize what is signal, and ideally what is the part of the signal that matters to the human. The hearing aid industry has been trying to do this for years, with limited success.
I think the sort of noise reduction we are talking about here essentially tries to decide which frequencies matter and which don't and eliminate the latter. However, it has to do this when what it is trying to identify as signal is hidden by noise.
In practice, I think what these systems achieve is increased user comfort, rather than recovering signal from noise, as humans are probably still a lot better at extracting signal from noise than algorithms, but they get tired in doing so.
One consequence of selective filtering will be a reduction in total audio power. I'd expect the total loudness to go down. I guess you could then renormalise, and increase the signal power to bring the total power up to the same level. However, most of are old enough to have a lot of high frequency hearing loss, so one may find that correction needed depends on specific hearing loss of the user and the original spectrum of the noise; one needs to renormalise the power as waited by the hearing sensitivity curve of the user. I imagine you would need, at least, a parameter to determine the degree of renormalisation.
Also, the more aggressive you make this sort of noise suppression, the more likely it is to have false positives, and suppress important frequencies. Also, the more aggressive you make it, the more you will get distortion as the result of modifying filter parameters on the fly.
Ultimately, though, the sort of noise that these systems are trying to remove is random in nature, so you can never be completely sure what is signal and what is noise.
(Hearing aids have a particularly difficult problem in that they are dealing with cocktail party noise, where the noise is the summation of lots of things that would, individually, be signals.)
(The ultimate noise reduction system would be one that recognized the speech and regenerated it, complete with characteristics of the original speaker. However, doing that really well can only be done by looking ahead several seconds, to be able to interpret meaning from what follows, as well as what precedes.)
As a caution, I believe the K3 has two different noise handling strategies: the one I am talking about here, and one designed to deal with impulse noise, where you simply cut out a short section of signal around the noise pulse.
-- David Woolley Owner K2 01623 On 12/01/2019 04:38, Mike Lichtman wrote:
I would like to see an improved Noise Reduction that doesn’t lower the volume or distort as much.
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