Vocal Reduction and Isolation
From Audacity Development Manual
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Vocal Reduction and Isolation attempts to remove or isolate center-panned audio from a stereo track. Vocals are sometimes (but not always) recorded in this way. The classic method achieves this by subtracting one Channel from the other, but the result will be (dual) mono. This method can still be found under Actions and is a quick way to remove the center if only mono is needed. All other "Remove" options in this effect preserve the stereo image.
The output of the Isolate options are (dual) mono and the narrowness of the center slice can be adjusted with the "Strength" slider. Center isolation is with the classic method not possible - it is the same as .
An Analyze function is included as well.
- See also the tutorial on Vocal Removal and Isolation
- Accessed by:
Action
- Remove Vocals: The default, removes the defined vocal range from the audio if it is center-panned and returns a stereo track.
- Isolate Vocals: Extracts the defined vocal range from the audio if it is center-panned and returns it as (dual) mono track.
- Isolate Vocals and Invert: Extracts the defined vocal range from the audio if it is center-panned and returns it as inverted (dual) mono track.
- Remove Center: Removes the whole frequency spectrum from the audio if it is center-panned and returns a true stereo track.
- Isolate Center: Extracts the whole frequency spectrum from the audio if it is center-panned and returns it as (dual) mono track.
- Isolate Center and Invert: Extracts the whole frequency spectrum from the audio if it is center-panned and returns it as inverted (dual) mono track.
- Remove Center Classic (Mono): Removes the whole frequency spectrum from the audio if it is center-panned and returns a (dual) mono track.
- Analyze: Tells you how big the chances for a successful vocal reduction/isolation are. It returns also the average Pan position for the selected audio. See below for an in-depth explanation.
Strength
The shape of the center is not a thin band but rather like a tent with a pole in the middle. This means that there will always audio from other pan positions be included. The Strength slider modifies the actual form.
Remove
- Less than 1.0: The notch has a V shape like a ship's keel, with a sharp point. Use this setting to preserve some amount of the center.
- 1.0 - the default: The notch has a V shape. The power distribution is preserved. The ideal setting for most cases.
- Greater than 1.0: The notch has a U shape. This removes also some adjacent audio to the center. Note that this won't remove stereo reverberation since it is distributed over the entire pan width.
Isolate
- Less than 1.0: The peak has a U shape upside down, like an arch. Only extreme left and right are eliminated.
- 1.0 - the default: The peak has a V shape, upside down. The power distribution is preserved. You might want a higher value when a lot of side audio leaks in. This is also the recommended setting when working with two tracks (options with ...and Invert).
- Greater than 1.0: The peak has a A shape like the Eiffel Tower , with a sharp point. This will attenuate most of the side energy but might produce artifacts or musical noise. Normalize the audio after using a high strength on isolation.
Low Cut for Vocal Range
All actions with Vocals use this value. The frequencies below will either not be removed or not included in the isolated audio. It is useful to exclude bass and kick drum. The default value of 120 Hz is good for most lead vocals, even low male voices. You can enter a higher value around 170 Hz for female voices and about 230 Hz for those of children.
High Cut for Vocal Range
All actions with Vocals use this value. The frequencies above will either not be removed or not included in the isolated audio. It is useful to exclude high sounds like bells, cymbals or high hat. Note that human sounds like S or Z can also be very high in frequency - 5000 to 8000 Hz, listen carefully to the preview.
Interpreting the analysis results
It is recommended to analyze the audio prior to the actual processing because it is very fast in comparison.
The two important values are:
- Pan Position
- This gives the average pan position for the whole selected audio. The value of the pan slider is not included in this calculation.
- Correlation
- This is a measure for the similarity of the two channels. Values of +/-100 mean that the channels are exactly the same, even if one is inverted. A value of 0 means no relationship. It is fruitless to attempt removal or isolation in these cases. The ideal value is normally around +50. Values below 0 are rather seldom and indicate that the stereo width is more than 100 %. Inverting one channel makes the correlation positive.
Sometimes, the lead vocals are not exactly in the middle. In this case, select a short portion of the audio where only the voice is audible and no other instrument. Choose Analyze. The correlation should be fairly high (around 100), this indicates that there is indeed only the voice.
You can now copy the value for the Pan Position. Paste it in the Pan dialog and reverse the sign, that is, put a minus sign in front of a positive value and vice versa. Mix and render the track. The voice will now be exactly centered and you can remove or isolate it. Don't forget to readjust the selection.
Limitations
- The input must be a true stereo file and not mere (dual) mono.
- Stereo Reverberation won't be fully removed because it is independently distributed over the whole stereo image.
- The whole processing is done in memory.
Long selections (over half an hour) might therefore cause Audacity to crash. - The plug-in does not know which kind of audio resides in the center, all is removed or isolated equally, be it vocals or bass or solo instruments.
Applications
*Creating a Karaoke version from an original song- Choose Remove Vocals if you want to keep some bass and drum beat.
- Creating an acapella version from an original song
- Choose Isolate Vocals with a high strength. The result has probably still some music in it. It is therefore better suited for a remix with a different accompaniment. Pure vocal versions have to be post-processed with other tools.
- Alternative to "Auto Duck" with pod casts
- Duplicate the track and choose Isolate Center and Invert on the second track. Record your voice. Silence the second track where you don't speak and the original music should be heard. On the same track, make fades at the boundaries (where the speech starts or stops).
- Removing excessive stereo reverb from a vocal or instrument track.
- use Isolate... to make a single vocal or instrument track "dry" again.
- Removing random system noise from a two channel recording of a mono source.
- use Isolate... to remove random noise produced by the soundcard, the cables or the computer itself.
- Removing single words or phrases
- You can remove offending content from a song or movie dialog by selecting it and choosing Remove Vocals. Mask it with other sounds, if necessary.
- Amplifying dialogs in a movie.
- Duplicate the track, isolate the vocals and adjust the gain.
- Converting stereo files into 3.1, 5.1 and other multi-channel formats.
- Duplicate the track and choose "Isolate Center and Invert" on the second track. Render all to a new track. Delete the first track, invert the second track and split the third track. Rearrange the tracks. accordingly. Thus you have "Front Left", "Center" and "Front Right" eventually.
- Extracting instrument solos
- Isolate the center if the solo is there, otherwise remove the center, split to mono and delete the superfluous track.
- Blending between original, karaoke version and vocals only
- Duplicate the track and choose Isolate Vocals and Invert on the second track. Choose the envelope tool or fade effects to gradually change from one mode to the other. Silencing the first track gives the vocals in isolation, silencing the second track gives the original and both tracks played together have the vocals removed.
- Correcting the pan position
- Analyze the whole track and copy the value for the pan position. Paste the value into the pan dialog and reverse the sign, that is, set a minus sign in front of positive values and vice versa.
- Measuring similarity between tracks
- Make the two (mono) tracks stereo and choose Analyze. The correlation value is the measure for the similarity in per cent.
- Applying a brick wall filter to mono tracks
- Duplicate a mono track, make it stereo and choose Isolate Vocals for band pass and Remove Vocals for band stop filtering. Adjust the frequencies accordingly.
The buttons
Clicking on the command buttons give the following results:
- gives a dropdown menu enabling you to manage presets for the tool and to see some detail about the tool. For details see Manage effects, generators and analyzers.
- plays a short preview of what the audio would sound like if the effect is applied with the current settings, without making actual changes to the audio. The length of preview is determined by your setting in , the default setting is 6 seconds.
- applies the effect to the selected audio with the current effect settings.
- aborts the effect and leaves the audio unchanged.
Links
