Audacity

Clicking and hissing sounds will always ruin a song or recording. Fortunately, with the right application, you can try to fix this problem, instead of deleting the audio files. A popular solution is Audacity, due to the vast range of tools it provides. Also, the application is free and open source and it is cross-platform. You can remove unwanted sounds from your audio tracks and make them sound much better, regardless if you are a Windows or Mac OS X user.

Once you import an audio file, Audacity will display wave forms, for the track's left and right channels, which can be edited together or separately. You may click and drag over a wave form, to select a specific segment, but you can also specify start and end points, to make a precise selection. A series of playback, volume and recording controls can be found on a toolbar, along with many other adjustment options. Selected segments can be trimmed, muted, copied, pasted and so on. Additionally, you can use an envelope tool on one or both wave forms, redraw individual samples and more.

Audacity provides a huge number of special effects, which can be found in the Effects menu, on the upper edge of the screen. Certain effects are applied immediately, without any further user input, while others require additional adjustments, on a separate window. With the available effects, a selected segment can be normalized, equalized, clicks and other unwanted noises can be removed and more. In addition, the software provides various analysis tools and it allows you to perform many other operations. Mixing and rendering, converting stereo to mono or resampling audio tracks are just a few examples.