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Unit 18: Rhythm

tend to allow more types of onsets (the consonants in a syllable before the vowel) and codas (the Notes
consonants in a syllable after the vowel), including complex onset and coda clusters, so will also
show more intervocalic durational variability than perceptually syllable-timed languages.
One of the major differences between the measures proposed by Ramus et al. and Low et al. is
their treatment of speech rate (see White and Mattys, in press, for a review). Ramus et al. build
speech rate into their measure by asking speakers of different languages to read utterances of
similar duration. Low et al., on the other hand, add a normalisation measure to their equations.
Specifically this normalisation is applied to vocalic intervals as these are considered to be most
affected by speech rate (Gay, 1978). Low et al. demonstrate that, of the two measures, the PVI is
more robust at different speaking rates.

Purpose
This paper aims to investigate the little studied area of rhythm in an RHD patient by applying the PVI.
As there are no PVI norms for Australian English the data from the patient with RHD will be compared
to that of a neurologically normal control. It is hypothesised that there may be some disruption to
rhythm in the speech of the RHD patient on the basis of studies which demonstrate deficits in other
aspects of prosody for this population. However, the direction of any change, be it to a more syllable
or stress-timed rhythm, is not clear. In addition, as rhythm is neither a linguistic or affective aspect of
prosody, and because there is no clear evidence that all aspects of prosody are right lateralised, it is
also possible that no effect will be found. This paper aims, therefore, to test whether there are any
differences between the rhythm of a person with RHD and a neurologically normal control, and to see
if any differences are in the direction of more syllable- or stress-timed rhythm.

Method
Participants
Participants were both males and native, monolingual speakers of Australian English. They had
both lived all their lives in Western Australia. Participants were matched on educational levels
with both participants having completed 12 years of education.
The recording of the control participant was collected in the participant's own home. He was 64 at
the time of the recording. The recording of the RHD participant was collected while the participant
was an inpatient in a rehabilitation hospital. He was aged 51 at the time of the recording. He had
suffered a large right middle cerebral artery ischaemic stroke 5 months prior to the recording.
Occupational therapy assessments at the time of the recording indicated that the participant had
reduced spatial awareness, left side neglect, difficulties with sequencing and reduced attention. The
participant was referred to the speech pathology department due to impaired prosody, inappropriate
topic choice, impaired discourse structure and tangential speech. The participant did not have any
history of, or present with any symptoms of, dysarthria. Initial assessments of prosody by the
speech pathologist indicated that although the client's prosody sounded impaired, measures of
intonation including pitch variation and mean pitch were within the normal range.

The task
The recordings used for this analysis were taken from a 30 minute structured conversation between
a speech pathologist and the participant. The speech pathologist was not known previously to the
participants. The conversation sample was collected for use in a larger study on the impact of
right hemisphere damage on gesture and prosody. For the purpose of this investigation only the
section of the discourse in which the participant was asked to describe an event that evoked a
positive emotion was analysed. The recordings were digitised using the acoustic analysis program
PRAAT 4.0 at a sampling rate of 11025Hz with 16bits of resolution.
Applying the PVI

The PVI works by firstly measuring the durations of vocalic and intervocalic intervals in a sample
of speech. So, for example, in the phrase 'the elephant ran' the first intervocalic (consonantal)

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