Question / Help Noise Suppression filter creating bad distortion

[cTnko]

Hi, i am not really sure if this should be classified as a bug, or i am simply missing something.

Basically, when i speak loudly into my microphone and Noise Suppression is enabled there is a rather bad distortion/clipping, this isn't happening with RearFir or with other filters that actually heavily modify gain (compressor - depends on the settings of course).

Ear rape warning!!!
I am attaching a recording where i "yell" into the microphone:

https://www.dropbox.com/s/wb362pfwhk4swnu/audio_distortion.mp3?dl=0

1 - without Noise Suppression filter
2 - with Noise Suppression filter (-20db)
3 - with RearFir in Subtract mode with already created noise profile

The only way i am able to improve the distortion is lowering the recording volume for the microphone quite heavily both on the mixing board and in windows, which obviously "breaks" optimal audio levels for in game VOIP, discord, etc...

Frequency analysis: http://imgur.com/a/LR8cC
Top = with Noise Suppression filter (-20db)
Bottom = with RearFir

The hardware that i am using:
Audio-Technica AT2020
Behringer XENYX X 1204 USB

Do you have any ideas what might be happening?

 

[cTnko]

bump

 

[Suslik V]

Try to apply Compressor filter with all default settings (10:1) but Output Gain of 9 dB before the Noise Suppression filter

 

[cTnko]

Thanks for the idea, tried it, sadly the distortion is still there but not as bad as before.

 

[Suslik V]

Then try to decrease Output Gain of the Compressor a bit.

 

[cTnko]

Yup, that certainly helps even more, i also had to lower the attack to 1ms to get rid of the initial "crack/spike", but doesn't this prove even more that the noise suppression doesn't work correctly?

I always thought the noise suppression needs to be applied before compressor (while the noise isn't as strong).

Or am i simply running into the case where my audio (without noise suppression) actually clips but it isn't audible, and noise suppression simply makes the matters worse?

 

[Simes]

Compression by default only squashes the loudest parts of a signal. What you probably want to do is have no additional gain on the compressor at all, so that the loudest parts are squashed and the quieter parts remain unchanged.

 

[cTnko]

So basically, have a "default" compressor, with attack of 1ms and output gain 0, to squash the loudest parts and then apply noise suppression, if i am correct this is the so called "compressor as limiter" setup?

Is adding an additional compressor or gain modifier after sound was already limited and noise suppressed an "ok" thing to do since the volume isn't as high as i would like?

 

[Simes]

"Compressor as Limiter" just means having a compressor with a very high compression ratio. Adding another compressor or gain boost afterwards shouldn't be too much of a problem; you probably only need to boost the gain in any case.

 

[cTnko]

Thanks guys, that did the trick, first "default" compressor with 0 gain and 1ms attack time, then noise suppression and then small gain modifier in the end.

I still find it odd that noise suppression "distorts" so much even when there is no audible clipping without it.

You learn something new every day :-)