Guide: Audio tools
Praat is a free software developed by the University of Amsterdam used to display, analyze, and edit audio files. We have used it in the lab to measure voice onset times, but it has many other uses. You can also write scripts within Praat to avoid manually analyzing files.
Praat is installed on one of the RA office computers (the right-most one furthest from the doorway?). Otherwise, it is free to download here. You do not need any activation key or license.
Here is an example of what Praat looks like with an audio file open:
A few basic functions
- Open/view audio files: When Praat is open, click the dropdown tab named ‘Open’ in the leftmost ‘Praat Objects’ box. Click either ‘Read from file’ or ‘Open long sound file’ (if the file is longer than a few minutes). Select your file. The name of the file will appear in the Praat Objects list—you can add multiple files to this list so you don’t have to go back and open each one individually. Then, highlight the file in the list you wish to work with and click ‘View and Edit’.
- Listen to all or part of a file: The grey bars at the bottom of the box (see image above) tell you how long a sound or section is and allows you to play it. The lowest bar, ‘Total duration’, is the length of the entire audio file in seconds; if you click this once, Praat will play the entire audio file. If you highlight a section of the audio by dragging a box with your mouse, or click somewhere in the file, new grey bars and times will appear, aligning with the sections you’ve created. Clicking one of these once will play the audio from only that section. For instance, if you clicked once on the grey box called ‘1.343628’, it would play the audio from 0 to the red line at 1.343628 seconds. If you clicked the right grey bar, it would play from 1.34628s to the end of the file.
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Zoom in: You can also zoom in on sounds to do more fine-grain analyses. To do this, you can either click the small box on the bottom left corner called ‘in’, then scroll to find the portion you’re looking for, OR highlight a segment of the file with your mouse and click the small box in the bottom left called ‘sel’ to zoom in on the highlighted portion. If you were to select and zoom in on the beginning of the utterance in the image above, it would look like this:
To zoom back out, click the small button that says ‘out’. - Crop: To crop an audio file, highlight the section you want to get rid of. Then, click the drop down tab, ‘Select’ at the top of the screen. Choose ‘Move start of selection to nearest zero crossing’. Then click ‘Select’ again- this time, click ‘Move end of selection to nearest zero crossing.’ Then, click ‘Edit’, then ‘Cut’. The sound file should be reduced to only the selected portion. Highlight the entire audio, click ‘File’, then ‘Extract selected sound (preserve times)’. This adds this new segment to the Object List. Then, in the list, highlight the new file, and click ‘Save’ on the top of the window, then ‘Save as .WAV file’ (usually, unless you want another file format.) You have to make sure to manually type “filename.WAV”; otherwise, it won’t save as a .WAV file. This creates a new file in the folder containing the parent file it was cropped from. If you name it with the same file name as the parent file, it will overwrite that file.
- Praat tutorials Very brief overview of a lot of basic Praat functions. More in-depth tutorial There are a lot of YouTube tutorials about Praat. I found this one helpful for learning how to determine VOT.
- Praat scripts: List of Praat scripts gathered by Google.
- Debug channel: Always an option.
MATLAB is a programming language/environment typically used for numerical computing.
If you are a student or faculty member, you can download MATLAB for free, here. You will need an installation key and an activation key, both of which can be found on this site.
HINT: Mind that you choose the correct keys for the year and version of MATLAB you choose to download!
- At the DoIt Tech Store, you can schedule a meeting with a MATLAB pro.
- The MATLAB YouTube channel has some training videos (if you scroll down far enough, there is a specific playlist for tutorials.)
Chronset is a program which detects voice onset times for short audio files, created by researchers at the Basque Center on Cognition, Brain, and Language.
There is an online platform. If preferred, you can download the source code from the same page, which needs to be run through MATLAB.
To use the online program, put up to 500 .WAV files in a ZIP folder with no subdirectory structure (i.e. no folders within the folder). Then, upload this folder to the Chronset site and enter your email address. You will eventually receive a .txt file attached to an email containing the names of your files and their VOTs (this may take up to an entire day depending on how many files you uploaded and how many are ahead of yours in the queue).
Upload specifications: .ZIP folder; no subdirectory structure; up to 500 short audio files (around 2-3 seconds); must be a .WAV file; folder must be less than 500MB in size.
MATLAB riddle: As of Summer 2017, we are currently working on making the offline source code for Chronset functional. Stay posted for updates.
The creators of Chronset can be reached via email at chronset@bcbl.eu.