Abstract
The aim of this study was twofold: to develop a method for
collecting voice data from natural working environments; and to
study loading changes. Changes caused by loading were approached from
two perspectives: the relationship between subjective complaints
and objectively measured voice features, and the changes of objective
variables during one working day.
Subjects consisted of female teachers from primary and secondary
schools. Six separate studies were carried out, the number of subjects
for each one ranging from 3 to 33. The subjects were 33 - 59 years
old. Recordings were made of their voices both during breaks and
lessons with a portable DAT recorder. The recordings made during
the breaks were collected on three days of one week, and four times
on each week. The speech samples of the lessons were taken from
the first and last lesson of the day. Subjects filled in a questionnaire
about their voice, which divided them into two groups: those with
few complaints (the FC group) and those with many complaints (the
MC group). In addition, three subjects performed a laboratory voice
loading task.
The speech sample recorded during breaks was a maximally sustained [a],
from which fundamental frequency (F0), jitter and shimmer were analyzed.
The lesson samples were analyzed for F0, its standard deviation
(F0 SD), sound pressure level (SPL), its standard deviation (SPL
SD), F0 time ( = active vibration time of the vocal folds)
and long-time average spectrum (LTAS). The laboratory samples (a
simple reading task) were measured for F0. Additionally, an index
(F0 x F0 time/ 1000) for assessing voice loading is presented.
The results showed that voice complaints correlated with objectively
measured voice features: the more the complaints, the higher the
F0 and SPL, the larger the F0 SD and the steeper the tilt of the LTAS,
the latter indicating that the voices of the MC group had a tendency
towards a hypofunctional voice usage. In addition, at the end of
the working week the shimmer values of the MC group were lower than
those of the FC group.
During the working day, the F0 rose, F0 SD and SPL SD increased
and the LTAS levelled out (changes towards a hyperfunctional voice
usage). Some of these changes are caused by the classroom situation,
some by the teachers themselves, and some (obviously the changes
of the F0 and the LTAS) by physiological alterations. Interestingly,
the main changes, which were the F0 rise and levelling of the spectrum,
occurred in the FC-group. The changes possibly reflect a normal
adaptation of the human body, and they may act as an alarm system
for avoiding excessive strain and exhaustion. The voice loading
index correlated with the voice complaints.
The experiment showed that the used method is well suited
for the measurement of voices in working places. The maximally sustained
phonation proved to be a suitable voice task for the measurement
of the voice in working places where subjects have to do a task
independently. The results also showed that F0 yields different
values in different conditions and with different voice tasks. This
deserves attention when defining standards for acoustic variables.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-5692-1 |
| Date | 08 June 2000 |
| Creators | Rantala, L. (Leena) |
| Publisher | Oulun yliopisto |
| Source Sets | University of Oulu |
| Language | Finnish |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 2000 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3205, info:eu-repo/semantics/altIdentifier/eissn/1796-2218 |
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