Nyquist Analyze Plug-ins

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These are optional plug-in effects for Audacity. They are written in the Nyquist programming language. To install Nyquist plug-ins, see this page in the Manual.

"Analyze Plug-ins" appear in the Audacity Analyze menu. Plug-ins that output text or labels will usually be in this menu.

Unless otherwise indicated, these plug-ins are released under the terms of the GNU General Public License.
 
Related article(s):
Warning icon Feedback and bug reports:
  • All new plug-ins added to this list are tested in the Audacity 2.x version current at the time, but many of the older plug-ins are still in need of testing.
  • Please also let us know which plug-ins you like and find useful as that will help us to develop the types of plug-ins that users want.


Contents


Downloading and Installing Plug-ins

Please see the Download Nyquist Plug-ins page.

Analyze Plug-ins

ACX Check

(Acx-check.ny) Download

Author: Will McCown

Based on code from the plug-ins: measurement.ny from endolith (at gmail.com) 2010-08 and in stats.ny from Steve Daulton.

This tool provides a number of useful statistics about the selected audio. Where appropriate values are reported both as linear numbers and in dBFS (dB relative to full scale). For each of the left and right tracks of the selection it will report:

Peak level The greatest absolute value in the selection
RMS level The RMS level of the total selection
NoiseFloor The RMS level of the quietest 500 milliseconds in the selection
RMS (A) The RMS level of the clip with an A-weighting filter applied
NoiseFloor (A) The noise floor of the clip with an A-weighting filter applied
DC offset The DC (overall average) of the selection, reported as a percentage of full scale.

The length of the selection is reported both in samples and in seconds.

The sample rate is also reported.

The Peak level, RMS level and noise floor results are compared against the published ACX requirements.

Limitations:

  • This tool is intended only as an aid in achieving ACX acceptance. A passing grade from this tool is NO guarantee of ACX acceptance.
  • This tool is very limited compared to the testing done by the ACX organization on submissions. In particular the noise floor measurement reported by this tool may be substantially lower than the actual noise floor. The intentional insertion of silence, or the overuse of noise reduction and compression tools will give you a passing number and yet will likely fail ACX acceptance.
  • A test clip without a sufficiently long "room tone" section may yield a false indication of a high noise floor.
  • Also beware that some noise sources are worse than others, and noise such as the 1000 Hz whine that often happens in USB audio interfaces may result in an ACX rejection even though it is below the -60 dBFS noise floor requirement.
  • The maximum permitted selection is 100 million samples (about 37 minutes at 44100 Hz sample rate).



Peak Finder rft

(Peakfinder-rft.ny) Download

Author: Edgar-rft.

Either places a single label at the first instance of a peak volume, or multiple labels at all the instances of that peak.

Parameters:

  1. Place labels at: [Choice: first peak only, all equally loud peaks (default)] The default setting will create labels for all peaks at the maximum absolute amplitude. "Absolute" amplitude disregards whether the value is positive or negative, so peaks may be up or down.
  2. Minimum Distance: [samples]: [1 to 1000, (default 100)] The minimum distance between labels (in samples). If audio is clipped there may be many samples in succession at the maximum amplitude. This setting avoids labeling every successive sample by setting a minimum distance between labels.

Limitations:

  • This effect can be very slow on long selections.
  • If the audio is clipped and "Place labels at: all equally loud peaks" is selected, there may be an extremely large number of labels created. The "Minimum Distance" setting is useful to reduce the number of labels.
  • Peaks that appear to be at the maximum amplitude will not be labeled unless they are exactly at the maximum amplitude.



Pitch Detect

(pitch-detect.ny) Download

Author: Steve Daulton

This plug-in attempts to detect and display the musical pitch and frequency of the selected note. In most cases the default settings will work best. The other options are provided to handle special cases such as analyzing synthetic signals that are outside of the usual musical range.

By default, the plug-in detects the pitch by analyzing the first 0.2 seconds of the selection. In most cases this should work well. If required the analyzed section can be set to the first part of the selection ranging from the first 10th of a second (0.1 seconds) up to one second.


Parameters:

  1. Frequency range: [Choice: 20-1000 Hz, 100-2000 Hz, 1 kHz-10 kHz. Default 100-2000 Hz] In most cases the default should be used as most musical pitches are in the range 100 to 2000 Hz.
  2. Analyse first (seconds): [0.1 to 1. Default 0.2] At the default setting the first 0.2 seconds of the selection will be analyzed.


Limitations: This plug-in is intended to detect single notes - you may get strange results if you try to analyze chords.

Extremely high frequencies may not be detected very accurately, especially if the sample rate is not very high. The plug-in will often detect very high frequencies better if the sample rate is 96000 Hz rather than 44100 Hz.

The plug-in should usually be able to detect pitches of single notes to within a few percent of the actual frequency. Don't expect the frequency in Hz to be exact..

Advanced usage tips:

  • For detecting very low frequencies (less than a few hundred Hz) the plug-in should be set to the low frequency range (20 to 1000 Hz).
  • For detecting very high frequencies (several kHz) the plug-in should be set to the high frequency range (1 kHz to 10 kHz).
  • For measuring synthesized tones and other electronic signals, the most accurate measure of frequency in Audacity is to use "Plot Spectrum" and set the "Size" setting to a high value.



Regular Interval Labels

(equalabl.ny) Download

Author: David R.Sky


Parameters:

  1. Label interval: [seconds]: Default sixty seconds between labels, from one second to six hundred seconds [ten minutes].
  2. Label text: The text that will appear in each label, default is "label".
  3. Prepend numbers to label text [0=no 1=yes]: Default is yes, so your labels would sequentially be "0label 1label..." and so on, using the default text.
  4. Final label: [0=exclude 1=include] Example; if your selection is sixty seconds long, and your label interval is ten seconds, the final label would be at the exact end of your selection. By default, the above variable is to exclude [not set] the final label.
  5. Final audio segment duration equal with others: [0=no 1=yes] Your label interval setting may result in the final segment of audio being unequal with the preceding ones. By default, the above variable is set to make the final audio segment equal in duration with the preceding ones. This might make the label interval slightly different from your chosen one, depending on the size of the final audio segment.

Users of screen readers: Labels may be viewed by opening the track menu [alt+t] and clicking on 'edit labels'. The labels and their time positions can be read by cursoring up and down and left-right. press alt+f4 to return to the main Audacity screen.


Released to the Audacity community June 25, 2007.

Thanks to:

  • Sami Jumppanen from the Audacity users group for suggesting this plug-in.
  • Leland Lucius from the Audacity development list for code feedback which helped wake me from late night programming! and thanks to Gale Andrews from the Audacity development list for suggesting improvements.
  • Alex S. Brown for example code from his silencemarker.ny plug-in for placing labels on the label track.



Selection Duration

(duration.ny) Download

Authors: David R.Sky, Steven Jones, Dominic Mazzoni

This plug-in gives the duration of audio you have selected, in either time units or samples as preferred. Current Audacity has a Selection Toolbar providing a screen-reader friendly display of selection start time and duration, but if you're using 1.2.x with a screen reader, this plug-in provides an easy solution. If you have opened or imported more than one track and have not yet done a Quick Mix, the duration of each track loaded into Audacity is given in the order it appears on the screen. Simply press ENTER after each track duration is given. The final screen gives information from Nyquist, which you can ignore. Simply press ENTER again to return to the regular Audacity screen.



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