Audio restoration

Audio restoration is the process of removing imperfections (such as hiss, impulse noise, crackle, wow and flutter, background noise, and mains hum) from sound recordings. Audio restoration can be performed directly on the recording medium (for example, washing a gramophone record with a cleansing solution), or on a digital representation of the recording using a computer (such as an AIFF or WAV file). Record restoration is a particular form of audio restoration that seeks to repair the sound of damaged gramophone records.

Modern audio restoration techniques are usually performed by digitizing an audio source from analog media, such as lacquer recordings, optical sources and magnetic tape. Once in the digital realm, recordings can be restored and cleaned up using dedicated, standalone digital processing units such as declickers, decracklers, dehissers and dialogue noise suppressors, or using digital audio workstations (DAWs). DAWs can perform various automated techniques to remove anomalies using algorithms to accomplish broadband denoising, declicking and decrackling, as well as removing buzzes and hums. Often audio engineers and sound editors use DAWs to manually remove "pops and ticks" from recordings, and the latest spectrographic 'retouching' techniques allow for the suppression or removal of discrete unwanted sounds. DAWs are capable of removing the smallest of anomalies, often without leaving artifacts and other evidence of their removal. Although fully automated solutions exist, audio restoration is sometimes a time-consuming process that requires skilled audio engineers with specific experience in music and film recording techniques.