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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_ f0 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_ f0 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 , 53 , 1227–1245. Bhuta, T., Patrick, L., & Garnett, J. D. (2004). Perceptual evaluation of voice quality and its correlation with acoustic measurements. Journal of Voice , 18 (3), 299–304. Boersma, P., & Weenink, D. (2010). PRAAT: Doing phonetics by computer (version 5.1.31). Amsterdam, Netherlands: Institute of Phonetic Sciences.

correlate with reduced PVI_Dur measures (see Discussion). The significantly reduced PVI_ f0 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 f0 on sustained ah . 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_ f0 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 f0 and standard deviation of f0 during sustained ah production were equivocal here. P1 had elevated average f0 , 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 ah sample. The average f0 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 ah . 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

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JCPSLP Volume 14, Number 3 2012

Journal of Clinical Practice in Speech-Language Pathology