Free noise reduction with Audacity

You may have a mp3 player that can record using a built in microphone or you may have a professional studio. When recording something sometimes you get noise on a recorded track. It can be anything from pink noise due to low quality devices in your signal chain, it might be hum from another electrical device or it might be a mechanical noise that your microphone picked up during recording. Can you get rid of the noise? Yes! Do you need expensive software to do so? Not neccessarily... enter the open source program Audacity.

Audacity is an audio editor available for Windows, OS X and Linux. You have access to recording, playback and editing multiple tracks. You can process, cut, copy, paste, merge, mix, add effects and import/export different audio file formats.

The first thing you have to do is (download and install Audacity if you haven’t done so already) record or open your noisy track in Audacity. If you have a pre recorded wma file you might have to convert the file. There are several free alternatives that do this. If you use Apple iTunes with Windows you already have the necessary software. You start by selecting a region of the audiofile that only contains the noise you want to get rid of. Then you select “Noise Removal” on the “Effect” drop-down menu. Then you click the “Get Noise Profile” button as the first step. Audacity will analyse the selected part of the audio file and close the window. The audio file has not changed at this point. Next you need to select the whole audio file (or the part where you want to remove the noise). Pressing ctrl+a (or Command+a on a mac) does this for you quicly. Next we go back to the “Effect” drop-down menu and select Noise Removal again. This time you alternate using the preview button and adjusting the sliders to get the result you want. When you are happy with what you hear you simply press the “Ok” button and the changes are made to your audio file. Finally you save the audio file in a format of your choice. Audacity lets you open and save files as WAV, AIFF, OGG, FLAC and MP3 (with Lame DLL installed.) Here you can hear the final result of my example file with the noise removed.

HP Pavilion DV1000 Laptop, Windows XP w/SP3, Audacity 1.3.5

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