JCPSLP vol 14 no 3 2012

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JCPSLP

Volume 14, Number 3 2012

Journal of Clinical Practice in Speech-Language Pathology

correlate with reduced PVI_Dur measures (see Discussion).

The significantly reduced PVI_

and PVI_dB values were

consistent with the perception of reduced pitch variability

and possibly low speaking volume.

Discussion

The aim of this study was to demonstrate the use of a small

set of acoustic measures of speech using accessible

software and readily executed measurements. By exploring

the relationships between various acoustic measures and

our perceptions of different aspects of speech and voice

quality, we can develop more objective and reliable

measures of change with time and with treatment. We can

also start to unpack the different acoustic signals that come

together to form our perceptions of, at times, more

wholistic constructs (Kent, 1997).

We predicted that the individuals with spastic or

flaccid dysarthria would demonstrate abnormal vocal

quality measures (e.g., jitter, shimmer, HNR), associated

with perceived abnormal quality. The individual with

ataxic dysarthria and pitch breaks and vocal tremor was

expected to show high variability of

on sustained

. All

participants were expected to have reduced speech rate

in diadochokinetic and connected speech tasks. Reduced

PVI_Dur should be associated with perception of equal

stress and reduced PVI_

and PVI_dB with perception of

reduced pitch and loudness variability in connected speech.

Vocal quality

HNR appears to be a useful indicator of abnormal vocal

quality (Bhuta et al., 2004; Kent et al., 2000; Yumoto &

Gould, 1982). It has been linked to hoarseness, although

here P1 and P3 were perceived to have strained-strangled

and breathy quality, respectively. It is possible that HNR is

useful as an indicator of pathology, rather than a specific

type, or alternatively that the different vocal quality

descriptors are difficult to differentiate in clinical practice

(Kreiman & Gerratt, 2000). As reported here, previous

studies have not found strong links between jitter and

shimmer measures and abnormal vocal quality (e.g., Bhuta,

et al., 2004; see Thompson-Ward & Theodoros, 1998).

Inclusion of HNR in a diagnostic protocol is worthwhile to

aid objective identification of abnormal quality or to track

changes with intervention, provided recording and

measurement methods are controlled across time points.

The measures of average

and standard deviation of

during sustained ah production were equivocal here.

P1 had elevated average

, counter to the tendency for

reduced pitch with laryngeal spasticity (Duffy, 2005). This

was not likely to be due to perceived mild pitch breaks,

as these were minimal during the

sample. The average

was 5.2 Hz outside the normal range; possibly the

threshold for perceiving high pitch does not correspond

precisely with the normal range. As predicted, the elevated

variability of P2 supported the perception of irregular pitch

breaks and vocal tremor in sustained

Speech rate and prosody

The measures of speech rate are by no means novel but

are made considerably easier within the visual spectro

graphic display of PRAAT. As reported numerous times, all

participants showed slowed rate in all tasks (Duffy, 2005).

The measures of prosody are less widespread. The PVI

is a useful measure that correlates well with perceptions

of stress production in words and connected speech

(Ballard et al., 2010; Low et al., 2000). Our hypotheses

were largely supported with equal stress and monopitch

and monoloudness reflected in reduced PVI values. Kim,

Hasegawa, and Perlman (2010) have reported similar

findings in spastic dysarthria from cerebral palsy. The lack

of a significant difference for PVI_

and PVI_dB for P1 and

P2 suggests that poor control over syllable/vowel duration

was mainly responsible for the perception of equal stress.

This result is not surprising for P2, as her irregular pitch and

loudness variations were distributed relatively randomly with

respect to the distribution of stress. P1 was perceived to

have monopitch and monoloudness, but this was not borne

out in the PVI measures.

P3 had significantly reduced PVI for all three measures.

While he was not perceived to have equal or excess stress,

the reduced duration variability may be related to perceived

vowel and consonant prolongations. Such prolongations

are also a feature of acquired apraxia of speech, with

these individuals disproportionately prolonging vowels

in unstressed syllables (Vergis & Ballard, 2012). P3 was

perceived to have

consistently

reduced pitch variation,

which appeared more related to PVI_

than the irregular

pitch variation of P1 and P3.

Conclusions

The aim of this paper was to demonstrate how some

acoustic measurements are within easy reach of standard

speech pathology clinics and can provide quick objective

measures for supporting diagnostic and treatment

decisions. While not all measures match squarely onto

perceptual constructs, there is value in exploring how

different acoustic features may combine to map onto more

holistic percepts. We must also be aware that the inherent

variability of the pathological speech signal and/or

limitations in applying a “generic” software algorithm to

pathological speech may at times yield inaccurate

measurements. The need to use a good quality

microphone, to ensure samples are collected in a quiet

environment, and to standardise recording and analysis

protocols across time points cannot be overstated.

The measures and methods presented here provide the

clinician with a starting point for documenting treatment

effectiveness and accountability in a less subjective manner

than using perceptual measures alone. We hope that,

by documenting some of these methods with illustrative

cases, we may encourage and facilitate translation of these

techniques into clinical practice (Graham et al., 2006) and,

over time, stimulate development of large normative and

patient databases for comparison.

Acknowledgments

The initial stage of this work was conducted while the first

two authors were employed as speech pathologists in the

Brain Injury Rehabilitation Service at the Royal Rehabilitation

Centre Sydney. We thank the three patients for their

participation in the study.

References

Ballard, K. J., Robin, D. A., McCabe, P., & McDonald, J.

(2010). Treating dysprosody in childhood apraxia of speech.

Journal of Speech, Language, and Hearing Research

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Bhuta, T., Patrick, L., & Garnett, J. D. (2004). Perceptual

evaluation of voice quality and its correlation with acoustic

measurements.

Journal of Voice

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Boersma, P., & Weenink, D. (2010).

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(version 5.1.31). Amsterdam,

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