Localizing Disturbances

When identifying the cause of audible distortions, you have to rely upon your ears and eyes:

Use audition tests to roughly localize the trouble area.

Try to spot disturbances in the selected area by visual inspection (look for any kind of disorder or irregularity in the signal waveform) or using special tools provided by DART XP Pro.

Pay extra attention to decisions made by the outlier detector - erroneous decisions might be the source of the problem.

There are several techniques of localizing disturbances you can try

Using different play commands

Set the time resolution factor to 50 or more and try different play options - use Play all, Play from the cursor and Play window for global (coarse) positioning, and Play block or Play local for fine tuning. Mark the suspect fragment and examine it more closely with increased time resolution.

NOTICE

The fragment played back when you pick Play local can be marked using the Select local block command accessible from the Edit menu.

Using frames

Framing a disturbance can be achieved by localizing it at the very beginning and at the very end of two partially overlapping fragments of the recording, respectively (if the disturbance is present in both segments it must be contained in their common area). To set a frame use the Set/Remove frame command available from the Edit menu.

Using frames

Using ‘smart editing’ tools

Smart mute, Smart cut and Crossfade cut utilities, available from the Smart editing group in the Toolbox menu, are useful and effective tools for localizing short-lived disturbances difficult to spot by other means. If after muting/cutting a specific fragment of the signal the disturbance is not audible it must be contained inside the selected block. Moreover, local muting and cutting are often the simplest ways of removing the unwanted artifacts. The success of the local muting/cutting technique depends critically on a careful selection of block boundaries, so as to avoid signal discontinuities usually heard as clicks. The smart editing tools make the search easy and the results quick to evaluate.

Smart mute

Smart cut

Crossfade cut

Viewing condensed signal plots

The overlooked noise pulses, as well as some large-scale disturbances, can be localized by examining condensed signal plots. Try choosing the time zoom coefficient in the range <4, 16>.

Examining time-frequency plots

If you have problems localizing a short-lived disturbance try analyzing the signal time-frequency spectrum in the vicinity of the trouble area. If any of the spectral graphs stands out from the neighboring ones the corresponding time frame is likely to contain the source of your problem.

Using 'Spectral view' to spot disturbances

Examining detection alarms

Many problems are caused by erroneous decisions of the outlier detector. Choose the Find bits command from the Edit menu (or press CTRL+F) to browse forward and backward through the detection file, looking for detection alarms of a specified length. Pay special attention to alarms covering more than 10 samples in a row.

Using the screen flash indicator

Each time the material actually shown in the active soundfile window is played, the screen flash indicator (situated in the central part of the toolbar) is on. By synchronizing the blink of this indicator with the occurrence of the alien sound, you can position disturbances with a high degree of precision (up to 1/16th of a second).

Using click markers

Click markers (available after choosing the Set click marker command from the Edit menu) are soundmarks which can be placed anywhere in a soundfile. You can use them for precise positioning of disturbances, e.g. you can use a pair of click markers to frame an extraneous sound.

Using click markers