In fact, the Praat software (Boersma and Weenink, 2009) can calculate five different measures of jitter and six different measures of shimmer. Now, as indicated above, there are many ways of calculating jitter and shimmer – each using a different formula. Clearly, any percentage score above these threshold figures is considered to be a sign of potential pathology. For example, the Multi-Dimensional Voice Program (MDVP) (Kay Elemetrics, 2008) indicates a threshold of pathology of <=1.040% for jitter and <=3.810% for shimmer (their parameters Jitt and Shim respectively). Thresholds of pathologyĭespite these complications, some authorities do declare so-called thresholds of pathology. In addition to this so-called voicing decision strategy, there will also be variation in the accuracy with which different programs can determine such things as the period and amplitude of a vocal signal. This may be, for example, because different programs use different methods for deciding whether an irregular part of the vocal signal is voiced or not. Measures of such things as jitter and shimmer using one software program cannot always be compared directly with measures made by another software program. variation in the equipment used, and – importantly – the use of different algorithms in the software programs which are used to make the measurements). what north Americans may consider to be within normal limits may be different from what north Koreans consider to be typical), and related to the testing environment (e.g. gender and age differences), cultural (e.g. There are many factors which militate against declaring all-encompassing norms. It is difficult to be precise about norms for acoustic measures such as jitter, shimmer, noise-to-harmonics ratio and fundamental frequency. You might want to check in your version what the default name is for an extracted sound.ĮDIT: Following suggestion, here is a revised version that uses an object ID to refer to the sound (I also replaced 'endeditor' with 'Close' so that it actually closes the editor window, and I dispensed with the selectObject command because I realized that the extracted sound object will already be selected): sound = Read from file: "sound.wav"Īs points out, the use of an object ID is more robust because it guarantees that you are selecting the exact sound you read in with the first method, if you have multiple objects with the same name in the object window you might select the wrong one.įollowing suggestion, here is an alternative that bypasses the editor window (the manual way to access the "Extract part" command is to highlight the sound in the object window and choose Convert > Extract part.): Read from file: "sound.wav"Įxtract part: 0.108, 0.I am really impressed with your site, but was wondering if you had any good references to obtain normative comparison for things such as jitter, shimmer, noise to harmonic ratio, and fundamental frequency. NOTE: In the latest version of Praat for Windows (5.4.12), extracted sounds are automatically named "Sound untitled", hence the penultimate line. The way it's written now, it's trying to apply the "Select" command to the object in the object window. You need to switch the "focus" of the commands to the editor.
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