I am using the Audacity noise removal tool to remove noise in the Audio.
i am using this tool right -
At first I select only a small part of only Noise, then I click on "get profile" and at the and i select all the Audio and run the tool again to remove the noise.
it work almost perfect.
this is my settings:
the Source before the filter:
in the before you can here Big noise and it sounds worse..
in the "after" the noise deleted perfectly but in high sounds there is strange phenomenon that i dot't know how to describe.
you just need to listen. it's importent that you listen on Headphones to be easier for you to notice that.
i know that if i will Increase the sensitivity to At least 17 then this phenomenon will not happen. but if i do this so i feel that it Damage the quality of the Audio and i don't want that.. on 0 it doasn't Damage the quality but this phenomenon occurs..
what i need to do to make it perfectly?
By the way,
this recording i made before this larn something on this post:
thanks for the helpers!
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You seem to be doing it correctly. Like most other audio/video filters, removing something you don't want generally effects something else you don't want it to.... so noise removal involves the same compromise. If it's the effect I think you're referring to, and I can't remember if there's a technical name for it, but it's like a kind of flanging/phasing effect, although I'm not sure I heard much of it in your samples (just using PC speakers at the moment).
One thing I did notice.... and there's no right or wrong, it's just personal preference..... the recording is fairly Lo-Fi to begin with and the noise removal does seem to have filtered out a little more of the higher frequencies. There's kind of two lots of noise..... a low "hum" and some higher frequency "hiss". The hum would drive me nuts, the hiss hardly bothers me at all. If it can't be done using the noise filter's own settings, I'd be tempted to experiment by taking a section of the audio which is only "noise" and use whatever EQ filtering Audacity has to filter out the higher frequency hiss, then use what's left (with any luck mainly hum) for the noise filter profile. The idea being to have the noise filter remove more hum than hiss to see if it'll also have less an effect on the higher frequencies in the audio itself. You'd probably not remove as much hiss either.... it's always a compromise and it's just an idea.... I guess you'd have to play around to see if it makes a difference.
You're not going to get 25 dB of noise reduction with good qualitiy. Shoot for 10 to 15 dB. And the better the source quality the better the results you'll get. MP3 already has a bunch of distortion that will only be exacerbated by this type of filtering. This hiss in the original might be better removed with a low pass filter.
ok.. i know the low pass filter but i sow that it is not alweys solve the noise.
so if it is "hiss" noise then i need to use the low pass filter and for "hum" i need the noise removal tool?
the low pass filter has deleted the noise perfectly
Audacity you'll see that the hiss noise is mostly above 8 KHz. There is little real signal above 8 KHz. A low pass filter with the knee set at ~8 KHz and a sharp rolloff does a pretty good job. It also eliminates the problem of the noise "breathing" with the loudness of the signal.
MP3 bitrate at -V0 max quality went down from 128 to 80 kbps with noise removed.
To the OP, in cases like this, noise is best left in there because it gives texture to dull recordings like this. Even if you remove it perfectly like I did, it sounds worse.