How Does Audio Clipping Occur?
In a real world situation, if you push a speaker beyond its capabilities, then the audio from it will be clipped -- this is sometimes referred to as overloading. This happens because there is a limit to the amount of power supplying the amplifier inside the speaker -- if the requirements go beyond this then the amplifier will clip the input signal. In this circumstance, instead of a smooth sine wave being produced for normal audio, a square waveform (clipped) will be outputted by the amplifier resulting in sound distortion.
Similarly in digital audio, there is also a limit on how far an input sound can be represented. If the amplitude of a signal goes beyond a digital system's limits then the rest of it will be discarded. This is particularly bad in digital audio as a large amount of definition can be lost through audio clipping.
Prevention is always better than cure and so it is always advisable to try and record digital audio by keeping the input signal within limits. However, if you already have digital audio files that you need to improve, then you can use certain audio tools to try and eliminate this as much as possible. Examples of audio software that can do this include:
- Software Media Players with Normalization -- some jukebox software players (iTunes, Windows Media Player, etc.) have a built-in normalization facility to process audio files that can prevent songs from being clipped.
- Standalone Normalization Tools -- these are third-party audio tools (many of them free) like MP3Gain which can be used to normalize the tracks in your music library. This will not only adjust the loudness of your songs so they (hopefully) all play at the same volume, but also reduce any audio clipping.
- Audio Editors -- this type of program provides many ways to digitally process an audio file. Audio editors such as Audacity have advanced algorithms for permanently removing clipping.
- MP3 Players with ReplayGain -- similar to software tools like MP3Gain, this feature is sometimes built into some hardware (MP3 players, PMPs). ReplayGain metadata can be useful for preventing very loud songs from being clipped by the hardware's internal digital to analog amplifier.
- CD/DVD Burning Software -- disc burning programs of this type often come with an option to normalize tracks especially when creating audio CDs suitable for playing on standard home entertainment equipment.