Reducing Noise in Digitized Disk and Tape Recordings

Opening up a pre-recorded WAV file in Cool Edit

1. Launch Cool Edit by right-clicking on the Cool96 icon on the desktop and selecting Open, or by clicking Start --> Programs --> Syntrillium --> Cool Edit 96. 

2. Click once on the two buttons for "Save ..." and "Filter and Noise reduction ..." and click OK.

3. Put the Digital Sound and Music CD-ROM into the computer's CD-ROM drive. 

4. Select File --> Open.  Click in the "Look in" menu at the top and select the CD drive (the icon looks like a round CD disk).

5. Look in the list for the folder named "Old Records".  Double-click on that folder or click on it once and click Open.

6. Click on the "Files of Type" menu and select "Windows PCM (*.wav).  This displays the WAV files in the folder.

7. Open (double-click on) "Frankie Carle - Cool Edit".

8. The waveform will be displayed.  To play it, press the spacebar, or click Play. Listen on your headphones so you can hear clearly. As the song plays, the cursor line moves through the waveform.

9. While the song is playing, click the In button to zoom in on the waveform and the Out button to zoom out.  Zooming in will allow you to see details more clearly.  You will be able to see the individual notes as they slide by.  You will also be able to see some pops and clicks as sharp spikes that stick out from the smoother music waveform.  These are caused by tiny scratches on the surface of the record.

Removing pops and clicks

1. Click the Full button to display the entire waveform, then click the Play button. As the song starts to play, click the In button two or three times until you can see the individual notes scrolling by as the music plays.  

2. When you hear a click that you want to remove, press the spacebar immediately to stop the song at that point. The portion of the waveform that was playing at that point is displayed in the center of the screen.

3. If you can see the click as a spike near the center of the screen, drag the mouse over two or three notes around that region and click the Zoom button to zoom in on that region. Click the Play button to play just that region. 

4. Carefully drag the mouse over the spike, so that only it is highlighted, and press the delete key on the keyboard. Click the mouse at the beginning of that region and press the spacebar (or click Play) to see if the click is removed. 

5.  Zoom out (click Out) a few times and press the spacebar (or click Play) to continue playing.

6. Select File --> Close and click No when it asks you if you want to "Save Changes...".

Automatic Noise Reduction

1. Select File --> Open --> double click on  "Frankie Carle - Cool Edit" 

2.  Drag the mouse over the first 10 seconds of the song and click the Zoom button. You should see section of "silence" that has only the background noise, e.g. the lead-in right before the music starts, followed by the first few notes of the song.

3. Select (drag the mouse over) the lead-in ("silence") before the music starts.  

4. Select Transform --> Noise reduction.

5. Click once on Get noise Profile from Selection.  

6. Click once on Close.

7. Pull down the Edit menu and select Select Entire Wave.  

8. Select Transform --> Noise reduction again.

9. Click OK.  The noise reduction process will take about 30 seconds to 1 minute for a single song.  When it is finished, play the song and compare to the original. 

10. To save the result, select File --> Save As... , make sure the "Save as type" menu at the bottom reads  "Windows PCM (*.wav)".  Type a new file name and click Save.

Try another song

1. Select File --> Open.  

2. Open (double-click on) "Cool Edit original".

3. The waveform will be displayed.  To play it, press the spacebar or click Play. (This is Nat King Cole's "Honeysuckle Rose", from his "Trio Days" album).

4. Try the Noise Reduction filter on this song. (Steps 2- 10 from the "Automatic Noise Reduction" section above).

Comparing other methods of recording

1. Click Start --> Programs --> Accessories --> Entertainment --> Windows Media Player. This is a general-purpose player application that is supplied with all Windows machines.  It can play most types of music, sound, and video files.

2. Click on the Now Playing tab on the upper left corner of the Windows Media Player window.  (If that's not showing, click on the little skinny "Show Taskbar" button on the left edge of the window)

3. Select File --> Open. If the File menu is not showing, click the tiny round button in the upper left.

3. Click in the "Look in" menu at the top and select "My Documents", then look for the "My Music" folder in the list and double-click it.

4. Look in the list for the "Old Records" folder.  Double-click on that folder or click on it once and click Open.

5. Several files are listed.  The following three files are original (unfiltered) recordings using three different recording programs and saved in three different sound file formats:

"MusicMatch original"	Recorded using MusicMatch 	MP3 format
"Cool Edit original"	Recorded using Cool Edit	WAV format
"Plus Analog Recorder original"  	Recorded using Analog Recorder	WMA format

To listen to one of these, click on it and click Open.  To listen to another version, select File --> Open.
 and repeat this procedure. Compare the three files listed above and see if you can hear any difference caused by the recording program or by the different formats they are recording in. (Most people can hear little or no difference).  Now open the file "Plus Analog Recorder reduced pops and hiss" and compare to "Plus Analog Recorder original".  This demonstrates Plus Analog Recorder's pop and hiss filter. 

If you have time, try opening and listening to some of the sound files in "Sound file examples" on the CD-ROM. Put your Sound and Music CD-ROM into the CD drive, select File --> Open, click in the "Look in" menu at the top and double-click the CD-ROM icon, then double-click "Sound file examples".  

(c) Tom O'Haver (to2@umail.umd.edu), March 2004