Walter F. Sendlmeier

EGG open quotient in aging voices—changes with increasing chronological age and its perception

This paper presents the results of open quotient (OQ) measurements in electroglottographic (EGG) signals of young (18–30 years) and elderly (60–82 years) male and female speakers. The paper further presents quantitative results of the relation between the EGG OQ and the perception of a speakers age. Higgins and Saxman found a decreased EGG OQ with increased age for females, while the EGG OQ increased for males as the speakers age increased in sustained vowel material 1. Although laryngeal degeneration due to increased age seems to occur to a lesser extent in females, the significant decrease of the OQ in elderly female voices could not be explained in terms of age-related physiological changes. Linville found increased spectral amplitudes in the region of F0 for the elderly (obtained by long-term average spectra (LTAS) measurements of read speech material), independent of gender, which could be indirectly interpreted as an increasing OQ 3. We measured the EGG OQ, not only for sustained vowels but also in vowels taken from isolated words and read speech material. To analyse the relation between breathiness in terms of an increased EGG OQ and the mean perceived age per stimulus, a perception test was carried out, in which listeners were asked to estimate speakers age based on sustained /a/-vowels varying in vocal effort (soft–normal–loud) during production. 1) The decreased EGG OQ for elderly females originally found by Higgins and Saxman 1 is not apparent in our data for sustained /a/-vowels; for males, however, we also found an increased EGG OQ for the elderly speakers. 2) In addition, an increased EGG OQ for the group of elderly in comparison to the younger males occurs for the unstressed syllable of the word material. 3) Our results show a strong positive relation between perceived age and EGG OQ in male vowel stimuli. Regarding 2), depending on the speech task at least a male speakers voice gets more breathy as age increases. Considering 3), increased breathiness may contribute to the listeners perception of increased age.

Feature, Phoneme, Syllable or Word: How Is Speech Mentally Represented?

Four experimental approaches frequently used in speech perception research are discussed with respect to their impact on word recognition models and their implicit assumptions on the mental representation of speech. These approaches are (1) reaction time experiments; (2) the procedure of click localisation; (3) the method of selective adaptation, and (4) the assessment of word similarities. The results of the studies vary as a function of the experimental procedure chosen. Phonetic features, single sounds, syllables and words as entities are alternatively favoured as primary perceptual units. A critical evaluation and an attempt at integrating the data lead to the assumption that the adult speaker/listener has different kinds of mental representation of speech at his/her disposal. Depending on the focus of perception, units of different sizes are primarily focused in the recognition process. This implies that the listener is able to modify his/her temporal analysis window to a certain extent. Nonetheless, as a default case, the syllable serves as the primary perceptual unit.

Speech cue enhancement in intervocalic stops

The place of articulation feature for stop consonants is subject to many errors in speech processing by hearing-impaired listeners. Attempts to improve the recognition of initial and final stop consonants by lowering the level of the first formant or-with a different approach-by narrowing the formant bandwidth of the first five formants only very partially led to satisfactory results. Intervocalic stops were used in the present investigation, on the one hand because the spectral information is represented twice (in the VC as well as in the CV-transition) and, on the other hand, because the closure duration offers additional information to the listener. The modification of bandwidth led to no noticeable improvement in the /b, d, g/ discrimination. A change of the closure durations affected the identification of the stops, especially the /b/. The modification of the transitions of the second and third formants optimized the recognition rates for /b/ and /g/.

Modification of strategies in feature extraction

A training procedure is described which seems appropriate to help severe to profound hearing-impaired subjects to make better use of their residual hearing. The training starts from the assumption that an auditory training is possible, which is based on the enhancement of certain acoustic cues that are still above threshold, but which are normally largely ignored by the listener. After the listener has become more sensitive to the enhanced cues, they are reduced in small steps until the original value of the stimulus is reached again. The results of a first try-out of the training procedure with hearing-impaired subjects are presented. The procedure with enhancement was found to be superior to a procedure not involving enhancement.

Primary perceptual units in word recognition

Results from different experiments concerning word similarity, word identification and manipulation of single sounds and findings from first language acquisition research are discussed as to their relevance for an understanding of which perceptual units are primary in word recognition. It is argued that units of different sizes may serve as primary perceptual units equally well depending on certain characteristics of the perceptual situation.