Acoustic Measures of Phonation

Question 1

Identify briefly what is measured by jitter perturbation

Answer 1

The cycle to cycle variation in F0 period (i.e. stability of vocal cord vibration)

Question 2

Identify briefly what is measured by shimmer perturbation

Answer 2

The cycle to cycle variation in peak amplitude

Question 3

Identfiy briefly what is measured by harmonics to noise ratio

Answer 3

The periodic component to sound divided by the noise component of sound. Low HNR reflects increased noise whilst high HNR reflects stronger periodic energy

Question 4

Identify briefly what is measured by degree of voice breaks

Answer 4

It measures the duration of the aperiodic sections in the vowel

Question 5

Identify briefly what is measured by cepstral peak prominence

Answer 5

CPP analyses the peak in the cepstrum that is present for voiced parts of speech

Question 6

What are the applications of jitter, shimmer, HNR, degree or voice breaks, and CPP in clinical practice

Answer 6

?

Question 7

Identify the limitations of jitter, shimmer, and HNR

Answer 7

1) These measures are not appropriate for meausreing aperiodic (i.e. dysphonic) voices, as the fluctuations oin frequency and amplitude in aperiodic voicing will give rise to inaccurate estimates of F0.
2) These measures are also highly dependant on optimal conditions of recording such as vocal intensity, vowel types, voice pathology, etc.

Question 8

Identify the factors that affect the accuracy of automatic measures of voice quality

Answer 8

1) Overlap in perturbation measures in normal speakers and those with voice disorders –> cut-offs of abnormality are sometimes crossed by normal speakers
2) High environmental noise increases measured levels of perturbation leading to false positives
3) High quality digitial recording equipment is required
4) Jitter measurement has an intrinsic error that is negatively correlated with sampling frequency.

Question 9

Identify the advantage of CPP when compared to conventional acoustic measures of voice quality

Answer 9

1) Less susceptible to the effects of background noise since it focuese on spectral instead of temporal domains
2) Is independant of F0 variations –> useful when analysing voices with pitch instability
3) Is sensitive to voice disorders –> changes in CPP shape and prominence can reflect alterations in vocal fold vibrations associated with disorders

Question 10

Identify 3 different approaches to assessing aperiodic voices using acoustic analysis software such as Praat

Answer 10

1) Measure perturbation during periodic portions of elongated vowel by only calculating jitter and shimmer when in range of expected minimimum F0
2) Degree of voice breaks (i.e. duraiton of aperiodic sections of the vowel)
3) Narrowband spectrogram as degree of periodicity can be judged via clearness of the spectrogram