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Note: Some portions of this tutorial were excerpted from the product literature

Here is information on the noise reduction program, Clear Voice Denoiser. Let me first mention that this is a program to be used in addition to your audio editing program (Audition, Wavepad etc). Clear Voice Denoiser has only one function, noise reduction, but it does it very well and it is easy to use.

This program is $49.95 for the registered version (available here) but you can download a full featured demo version with no expiration date here. The demo version is limited to a maximum time length of 30 seconds which will be more than long enough for many of the EVP you'll capture. I liked the program so much that I eventually bought it in order to be able to process longer recording sessions without having to break them into smaller segments first.

The Denoiser is really useful for removing the top layer of noise that occurs with any recording. One pass through the Denoiser at the default noise reduction settings often reveals whispers, low voices and other sounds not heard before applying the reduction. One caution however. Noise reduction, while clarifying the original message and revealing new ones can also tend to change the pitch of the original voice and even alter the words of the original message beyond recognition. As long as the original clip is available for comparison, this will not be an issue since the reduction can be reapplied to achieve the necessary balance between clarity and the original intent of the message.

Note: There are no system requirements listed on the website, so be sure to try the Demo before purchasing the program to insure it is compatible with your operating system

Using the Clear Voice Denoiser Program:

   1. After working with your audio editing program to load, edit and save a file, open the Denoiser program and load the file you intend to use. You do this by clicking "Load Source" (see Figure 1 and 2). The Denoiser only accepts “wav” files, so if you have a “mp3” file, you will have to convert back to *.wav first. Although you can not see this in the attachment, when you first open the program, the "Load Source" button will be flashing and highlighted in green. This is a nice feature of this program and you will notice it on different buttons as you proceed through the steps. It is used to guide you as to which buttons are functional at each specific point in the noise reduction process.
   2. After you have chosen the file, you will see it open in the Denoiser processing window (see Figure 3). You can play the original (click "Play Source") if you want to verify you have chosen the correct file, or you can go directly to applying noise reduction. This is accomplished by clicking on the "Clean" button which will be flashing and highlighted in green. However, you may also want to choose the level of noise reduction you want to apply to your file.


The Denoiser program opens with a default setting of "4 normal" 17db or 18db. You can adjust this to soft or hard (see the slide bar above the process window). Use caution, however, because even the default settings, while reducing background noise, can change the tone and even alter the words of the original message. Any changes that occur using the default setting are usually slight and still allow the listener to hear the entire message, while reducing the noise enough to hear additional sounds and voices that may have been captured but were inaudible before applying noise reduction. Once you have decided on a setting click "Clean" and the process will begin. You can track the progress of the cleaning by looking at the box labeled "Process Info" (right side, above process window, see Figure 4). When the blue line moving from left to right completes, the process is just about finished. Once it is totally complete the process window display will change from the original green form to a green and blue form (see Figure 5).

   3. At this point you can choose "Play Source" to hear the original or "Play Target" to hear the noise reduced version you just created. Regarding saving the new file, the Denoiser program saves it automatically in the same directory as the original file. It does this by adding the extension “_CLR” to the name of the original file. When you return to Audition to continue editing the file you will now see the original file and the noise reduced version (see Figure 2 for an example).