Workflow for Removing Noise with Audacity

Suggested Workflow for Removing Noise with Audacity

In Audacity you can remove any kind of unwanted noise using the Remove Noise effect. These noises might include the popping sounds recorded when pronouncing the letter “p” or “b”, the sound of an air conditioner running in the background, the sibilant sounds often picked up when pronouncing the letter “s,” etc. In this brief tutorial I will detail a noise removal workflow I developed from my experiences in removing extraneous noises from hundreds of audio clips. I am assuming that the reader is familiar with the basics of Audacity, a free audio editing program. If you have never used Audacity, or need a refresher, I posted a tutorial covering the basic features of the program at this website: http://irt.austincc.edu/Audio/ . Let’s get started:
1. Import a clip into Audacity, using File > Import Clip or by holding down Control (Command on Mac) + Shift + I on a Windows keyboard.

2. Play the entire clip, noting the areas where there is noise. Vertical lines (|) indicate noise, usually created when the person who recorded the clip recorded the letter “p” or “b.” Figure 1 below shows what noise created when recording the letter “p” typically looks like.

3. Zoom in on the timeline to get a better look at the noise you want to remove by pressing Ctrl + 1 on the keyboard twice.

4. Select the first area with noise you want to remove. Don’t select only the noise. Select a second or two or audio before and after the part with the unwanted noise.

5. Press the space bar or the Play button and listen to the area you have selected. If the noise was created when pronouncing the letter “p” you should hear a “pppp” sound.

6. Select only the noisy area this time and listen to it. Areas of noise created when recording spoken speech are usually “p” or “b” sounds. As stated in Step 5, noise associated with the letter “p” will usually sound something like “ppppp.” Often when we record the word, between, you will hear something like “twtwtwtw.”

7. Now, we are ready to remove the noise we selected. In Audacity this is a two-step process.
7.1 From the menu at the top of the Audacity interface select Effect > Remove Noise. 7.2 Select Get Noise Profile. 7.2.1 Usually we want to reduce the noise by 24 DB (decibels) 7.2.2 Set the Sensitivity to 0.00. 7.2.3 Frequency Smoothing – 520 Hz is the default. Usually we don’t need to change this. When you
remove the noise and listen to the cleaned up area if it doesn’t sound good you may need to adjust this setting. 7.2.4 Attack / Delay Time – 0.00 is the default. I never adjust this setting. 7.2.5 Click OK.
7.3 Select Effect > Remove Noise again. 7.3.1 Do not change any settings. Click OK to remove the noise. The area that had noise should now be flattened.

8. Scroll through all the other areas of the sound wave or wave form that have noise and repeat Steps 4-7 to remove them.

9. Zoom back to the normal view of your clip by pressing the Ctrl + 2 keys or View > Zoom Normal on the keyboard.

10. Skip to the start of the clip by clicking on the Zoom to Start button ,, or by selecting View > Zoom Normal on the menu and listen to the entire sound clip again.
11. Remove any areas of noise you might have missed when executing Steps 4-7.

12. Select the entire clip by pressing Ctrl + A on the keyboard or by selecting Edit > Select > All on the menu.

13. Now, we are going to normalize the clip. Normalization boosts the sound to the loudest decibel level possible without clipping, or truncating, the highest sounds in the recording. From the menu select Effect > Normalize. 13.1 Accept the default settings. 13.2 Click OK.

14. Listen to the entire clip again to make sure it sounds good.

15. Sometimes when we normalize an audio clip we introduce additional noise. If this is the case, follow steps 4-7 to remove it.

16. The final step is to export the clip as an MP3 file. 16.1 Select File > Export or press Ctrl + E on the keyboard. 16.2 Save your clip in the location where you wish to store it. 16.3 It is a good idea to follow a systematic naming convention that makes it easy to identify what you have done to each clip. For example, I give my edited audio clips file names such as: Module_2_Slide_1_Edited.

NOTE: When I insert images into this post they are unrecognizable. You can view the document with the images inserted at this site:

http://irt.austincc.edu/Audio/noiseremovalworkflow.pdf

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