HI-SIMv1.0--towards the virtual reality of hearing impairments.

The virtual reality of hearing impairments has obvious practical applications in areas such as audiology, speech therapy and hearing aid technology and serves as an informational tool for the family members of the hearing impaired. To simulate hearing impairment, a CD-ROM with filtered speech material accessible through a graphical user-interface was produced; the user-interface was created with standard multimedia tools. The CD-ROM, HI-SIMv1.0, intended as an interactive educational tool, offers a virtual experience of the effects of a selection of common types of hearing impairment. The options available in this simulation include grade of hearing impairment, audiometric configuration and the type and level of background noise. Word recognition scores can be computed for standard Finnish audiometric material.

Can the impact of hearing impairments be modelled?

The effects of two simulated hearing impairments (presbyacusis) on speech perception were investigated in two groups of normally hearing subjects (30 and 48 subjects, respectively). Eight patients with presbyacusis with similar hearing impairment to those in the latter simulation served as the clinical material. Word recognition scores were measured in quiet and in cocktail party noise (S/N + 18 dB and + 12 dB). The recognition scores deteriorated in the less favourable listening conditions. Somewhat surprisingly, the hearing impaired subjects showed better word recognition scores in quiet and especially in moderate noise. Subjective complaints on speech perception difficulties in noise on a visual analogue scale behaved quite logically; the hearing impaired subjects' subjective experiences were no milder than those of the normally hearing during the simulation. The better results in word recognition shown by the hearing aid candidates may be explained by habituation to the hearing impairment.

Working-day effects on the spectral characteristics of teaching voice.

Ten teachers made recordings during one normal working day using a portable DAT recorder and a head-mounted microphone. In addition, the subjects filled in a questionnaire of signs of vocal fatigue. The speech samples were selected from the first and last lesson from three points representing the beginning, middle and end part of the lesson, respectively. To standardize the samples, 30 [a] vowels from stressed syllables were chosen for spectral analysis. The level of the fundamental and second formant regions (L1), the level of frequency ranges 2-5 kHz (L2) and 5-10 kHz (L5) were measured. From these measurements the parameters L1-L0, L1-L2 and L1-L5 were formed and used in the analyses as well as the energy levels below and above 1 kHz (alpha). Statistically significant changes were observed in the following parameters: the L1-L2 and L1-L5 differences, and the alpha ratio. In general, there was an increase in the energy content of the high frequency components due to vocal loading. The subjective reports revealed a statistically significant relationship with the spectral characteristics.

External laryngeal frame function in voice production revisited: a review.

Research indicates significant contribution of extrinsic laryngeal mechanisms to voice production. This article reviews the major theories of the role of the external laryngeal factors in voice production and relevant experimental data. The review suggests that partly neglected external factors and possibly even misinterpretation of some of the recently documented individual variation in physiological data may have unnecessarily complicated the issues pertaining to the interplay between the physiological mechanisms of the larynx. The implications of contemporary findings and documentation in the modeling of the extrinsic factors are discussed and a synthesis of empirical data into two simple models of the extrinsic forces of pitch control is presented. Also suggested by the review, a basic principle, probably underlying the laryngeal control of phonation, is put forward.