Freesound Forums

I'm having this problem with my new microphone where the wave form isn't centered
see here http://i48.tinypic.com/1hqxhh.png
with certain speaker it emits a really annoying constant beep sound
does anyone have an idea how to fix this?

I think that is known as DC offset. There could be several problems, but you have omitted some important info like Microphone type, cable, soundcard, etc.

Yep, that's a DC offset. Cheap soundcards of the old days had problems with it. And maybe some built-in have them still.

Two ways how to get rid of it.

1) There is DC offset removal tool in stereo editor like Soundforge. It shifts the wave by specified amount (amount which can be detected by the tool).
2) Hipass filter in your EQ. Because DC offset could be interpreted like a 0Hz tone and hipass filter filters out low frequencies under specified number. 20Hz should do it.

ok thanks... I've fixed the problem I'm just not sure how to fix already recorded sounds...
none of my programs seems to have an option like that... i'm using an old version of cooledit pro 2.0

There should be hipass filter in cooledit. Does it have support for VST? If it does you can use some freeware, like http://www.ddmf.eu/freeware.php ... sometimes hipass filter is called low-cut, and that's the case with DDMF colour EQ.

From the manual:

DC Offset–
Many sound cards record with a slight DC offset, which means that direct current is introduced into thesignal by the card, causing the center of the waveform to be off from the zero point in the waveform display. This is seen as the waveform being “shifted” above or below the center line in the Wave Display, and can cause a click or pop to be played at the beginning and the end of the file. To compensate for DC Offset, you can choose the DCBias Adjust setting in
Effects > Amplitude > Amplify