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Quick noise removal with Audacity

During JCrete conference, every session was recorded onto a small audio recorder that was standing in the middle of the room. Obviously, you can’t expect good sound quality when people are making all kinds of noises. Such recorders require a decent amount of post processing, which takes time, which no one has. Below are some simple steps describing how to lower the noise and amplify the audio level with a free program Audacity.

1. Download and install Audacity and LAME MP3 encoder.
2. Start Audacity and import your audio file using the menu File | Import.
3. You’ll see the graphics of the audio tracks.
4. Now you need to identify the noise to be filtered out from the audio. Several times hit the button on the toolbar that looks like the looking glass with the plus sign to zoom in.
5. Highlight a 2-3 seconds fragment with the noise only.
6. Select the menu Effects | Noise Removal and press the button “Get Noise Profile” so Audacity knows what to remove from the recording.
7. Click anywhere on the track to unhighlight the sound fragment.
8. Select the menu Effects | Noise Removal again, but this time just press the button OK. Audacity will start processing your audio removing the audio sample that matches your selection from step 6.
9. If there is still some noise GO TO step 5. If you don’t like the results of the second noise removal, select the menu Edit | Undo Noise Removal.
10. Amplify the sound level by selecting the menu Effects | Amplify. Enter a number (e.g. 5) and check off the box Allow Clipping.
11. If you want to remove unwanted noisy fragments, just highlight it and hit the button Delete on the keyboard.
12. Save the new version of MP3 by selecting the menu File | Export. Pick the mp3 format. Save it as a Joint Stereo and select the rate 32kbps, which is sufficient for the speach recording in a non-audio-friendly studio, and the file size won’t be too big.


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More Stories By Yakov Fain

Yakov Fain is a co-founder of two software companies: Farata Systems and SuranceBay. He authored several technical books and lots of articles on software development. Yakov is Java Champion (https://java-champions.java.net). He leads leads Princeton Java Users Group. Two of Yakov's books will go in print this year: "Enterprise Web Development" (O'Reilly) and "Java For Kids" (No Starch Press).