Forums

amplify without increase of noise

Started by StefanF February 14, 2007
Hi!
I have a recorded file (wav) where the recorded signal is very weak. When
I try to aplify the signal the signal is almost lost in all the noise
(mostly high frequency) that also seems to be added from nowhere... maybe
it is "white noise"? Are there any program (not expensive) that can can
remove this unwanted noise from the file?



By 'amplify' do you mean to scale the numbers up before you play them
out, or turn up an analog volume control?

Dirk

On Feb 14, 10:17 am, "StefanF" <stefan.fr...@passagen.se> wrote:
> Hi! > I have a recorded file (wav) where the recorded signal is very weak. When > I try to aplify the signal the signal is almost lost in all the noise > (mostly high frequency) that also seems to be added from nowhere... maybe > it is "white noise"? Are there any program (not expensive) that can can > remove this unwanted noise from the file?
Stefan,

There is a consumer application called SoundSoap which may be suitable 
for you:

http://www.bias-inc.com/products/soundsoap/

Answering the question of whether "is it white noise" may require some 
additional signal processing involving analysis of the signal spectrum.

There are some MATLAB .m files available on the Internet and various 
algorithms which can be used to remove white noise.

Nicholas


In article <CKqdnYobXa6GtU7YnZ2dnUVZ_oSnnZ2d@giganews.com>, 
stefan.fritz@passagen.se says...
> Hi! > I have a recorded file (wav) where the recorded signal is very weak. When > I try to aplify the signal the signal is almost lost in all the noise > (mostly high frequency) that also seems to be added from nowhere... maybe > it is "white noise"? Are there any program (not expensive) that can can > remove this unwanted noise from the file? > > > >
On Feb 14, 11:09 am, "dbell" <bellda2...@cox.net> wrote:
> By 'amplify' do you mean to scale the numbers up before you play them > out, or turn up an analog volume control? > > Dirk
Also, how are your playing the data out? Dirk
> > On Feb 14, 10:17 am, "StefanF" <stefan.fr...@passagen.se> wrote: > > > > > Hi! > > I have a recorded file (wav) where the recorded signal is very weak. When > > I try to aplify the signal the signal is almost lost in all the noise > > (mostly high frequency) that also seems to be added from nowhere... maybe > > it is "white noise"? Are there any program (not expensive) that can can > > remove this unwanted noise from the file?- Hide quoted text - > > - Show quoted text -
>Stefan, > >There is a consumer application called SoundSoap which may be suitable >for you: > >http://www.bias-inc.com/products/soundsoap/ > >Answering the question of whether "is it white noise" may require some >additional signal processing involving analysis of the signal spectrum. > >There are some MATLAB .m files available on the Internet and various >algorithms which can be used to remove white noise. > >Nicholas > > >In article <CKqdnYobXa6GtU7YnZ2dnUVZ_oSnnZ2d@giganews.com>, >stefan.fritz@passagen.se says... >> Hi! >> I have a recorded file (wav) where the recorded signal is very weak.
When
>> I try to aplify the signal the signal is almost lost in all the noise >> (mostly high frequency) that also seems to be added from nowhere...
maybe
>> it is "white noise"? Are there any program (not expensive) that can
can
>> remove this unwanted noise from the file? >> >> >> >> >
Thanks for your replies! I looked at SoundSoap, and it looks interesting. But there doesn&#2013266066;t seem to be any trial version, and it would be nice to be able to see if it can do what I want before I buy the product. Dirk, what I want to do is to increase the volume since the actual sound I am interested in is quite silent, if you know what I mean. But when I do it with for example an equalizer, lots of "noise" is also added (or amplified). The sound is recorded with an mp3 player, so of course the quality is not so good to begin with. So the question is if it is possible to enhance the quality (reducing the "white noise) without totally destroying the target signal, which is quite weak.
On Feb 15, 6:16 am, "StefanF" <stefan.fr...@passagen.se> wrote:
> >Stefan, > > >There is a consumer application called SoundSoap which may be suitable > >for you: > > >http://www.bias-inc.com/products/soundsoap/ > > >Answering the question of whether "is it white noise" may require some > >additional signal processing involving analysis of the signal spectrum. > > >There are some MATLAB .m files available on the Internet and various > >algorithms which can be used to remove white noise. > > >Nicholas > > >In article <CKqdnYobXa6GtU7YnZ2dnUVZ_oSnn...@giganews.com>, > >stefan.fr...@passagen.se says... > >> Hi! > >> I have a recorded file (wav) where the recorded signal is very weak. > When > >> I try to aplify the signal the signal is almost lost in all the noise > >> (mostly high frequency) that also seems to be added from nowhere... > maybe > >> it is "white noise"? Are there any program (not expensive) that can > can > >> remove this unwanted noise from the file? > > Thanks for your replies! I looked at SoundSoap, and it looks interesting. > But there doesn't seem to be any trial version, and it would be nice to be > able to see if it can do what I want before I buy the product. > Dirk, what I want to do is to increase the volume since the actual sound I > am interested in is quite silent, if you know what I mean. But when I do it > with for example an equalizer, lots of "noise" is also added (or > amplified). The sound is recorded with an mp3 player, so of course the > quality is not so good to begin with. So the question is if it is possible > to enhance the quality (reducing the "white noise) without totally > destroying the target signal, which is quite weak.- Hide quoted text - > > - Show quoted text -
Are you running the low-level signal through the equalizer, converting it to integer and then amplifying it, possibly converting it to integer again? Again, you didn't say how you were amplifying it and playing it out as a wave file? Playing it with what? Dirk
Stefan,
Is your signal bandlimited?  Then you could simply attenuate the
frequencies before amplifying the signal, which is equivalent to
adjusting your eq levels.  In order to determine the "whiteness" of
your noise you would have to look at the power spectral density.
White noise has a flat PSD, which means the noise signal is
uncorrelated in time.  Denoising is a large area of signal
processing.  Are you just looking for a prepackaged software solution,
or do you have access to something like Matlab?

What OS are you using?  There are many open-source programs which can
clean up your wave file.  If you're a linux user try the Gnome Wave
Cleaner

http://gwc.sourceforge.net/

-Marc

StefanF wrote:

> Dirk, what I want to do is to increase the volume since the actual sound I > am interested in is quite silent, if you know what I mean. But when I do > it with for example an equalizer, lots of "noise" is also added (or > amplified). The sound is recorded with an mp3 player, so of course the > quality is not so good to begin with. So the question is if it is possible > to enhance the quality (reducing the "white noise) without totally > destroying the target signal, which is quite weak.
You must amplify the signal before it is recorded. Use a high quality preamplifier (either standalone or in a mixing console) and chose the proper microphone (if we talk about audio). If you tell us what you want to record you can get more help. bye Andreas -- Andreas H&#2013266172;nnebeck | email: acmh@gmx.de ----- privat ---- | www : http://www.huennebeck-online.de Fax/Anrufbeantworter: 0721/151-284301 GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc