Restoring a Soundfile

Overview

Archive recordings are corrupted with many different kinds of disturbances. Among the most frequently encountered ones are impulsive disturbances (such as clicks, pops and record scratches), wideband noise (such as a tape hiss or surface noise of vinyl records) and harmonic disturbances (such as the power line hum). DART XP Pro offers several tools for noise eradication, all available from the Restore menu.

DeClick Plus is a procedure for elimination of impulsive disturbances and low intensity wideband noise. Based on indications of an outlier detector - a device, which searches for noise pulses - the system isolates and reconstructs the irrevocably distorted signal samples.

ReTouch allows one to use the renovation program in the "manual" declicking mode, e.g., to overrule decisions made by the outlier detector in the automatic detection (DeClick Plus) mode. By editing the so-called detection files (created by the system during declicking) you can set, cancel or modify detection alarms forcing the system to remove overlooked noise pulses and/or to preserve without changes some genuine signal features misclassified as outliers. A powerful function provided by ReTouch is replacement/reconstruction of fairly large fragments of the sound material, which is useful when coping with some long-lasting disturbances or dropouts.

DeNoise Plus is a procedure for elimination of a broadband noise of known characteristics. Prior to using this function you have to "noiseprint" an audio file, i.e. to run a special noise identification function (NoisePrint) on a fragment of the recording that contains noise only - a short piece of "silence" preceding or coming after the recorded signal can be used for this purpose. Alternatively, if the reference noise sample can't be indicated, you can try using a noiseprint extracted from another archive recording (preferably coming from the same source, e.g., from the same old record).

DeHiss Plus is a wideband noise reduction utility based on a standard noise model. You can use it when a noiseprint is not available. If noise characteristics are time-varying DeHiss Plus may yield better results than DeNoise Plus - being less selective it is also less sensitive to changes in the noise profile.

Even though DeNoise Plus and DeHiss Plus were not designed to cope with impulsive disturbances, both are capable of reducing clicks (small clicks are completely eliminated in the process of removing wideband noise; the large ones are reduced in size).

DeHum is a tool for elimination of harmonic disturbances.

Finally, Filter builder allows you to define and realize (MyFilter) complex restoration tasks such as combined declicking and denoising, for example.

If your computer is sufficiently fast to keep up with the flow of the input audio data, choose the Real-time command from the Restore menu and select the desired processing option. When operated in the real-time mode, DART XP Pro processes the input audio data ‘on the fly’, without saving them to a hard disk prior to restoration. If you connect a recording device to the output of your audio card you will be able to save the restoration results directly to the external medium without engaging the computer hard disk at all !

The following two-pass procedure is strongly recommended for high quality restoration

1. Use DeClick Plus/ReTouch to remove clicks, pops and scratches from an archive recording.

2. Use DeNoise Plus/DeHiss Plus to remove the wideband noise.

Elimination of impulsive disturbances

Retouching a soundfile

Elimination of broadband noise

Elimination of harmonic noise

Tuning restoration utilities

Real-time restoration

Advanced restoration techniques

Rules of soundfile management

If you register the original archive soundfile as a root soundfile, the DART XP Pro librarian, called the Soundfile Manager, will help you organize and keep track of all renovation experiments involving that file.

Based on your indications, the Soundfile Manager automatically updates the names under which the renovated soundfiles are saved. Moreover, it creates and updates special database files containing information about all files derived from a specific root file. The resulting family trees of soundfiles, called audio trees, are ideal tools for quick revision and comparison of different variants of processing.

Even though we strongly encourage you to register soundfiles, you are free not to do it. When working with unregistered files, you can use all DART XP Pro functions and utilities except those provided by the Soundfile Manager. In particular, if you do not use Soundfile Manager, you must look after the names of created soundfiles and maintain the tracking of their content, processing details etc.

Registering a soundfile

Managing registered soundfiles

Managing unregistered soundfiles