A well-functioning voice is an essential tool for one third of the labour force. Vocal demands vary to a great extent between the different voice and speech professions. In professions with heavy vocal loading (e.g. school and kindergarten teachers), occupational voice disorders threatening working ability are common. Vocal loading is a combination of prolonged voice use and additional loading factors (e.g. background noise, acoustics, air quality) affecting the fundamental frequency, type and loudness of phonation or the vibratory characteristics of the vocal folds as well as the external frame of the larynx. The prevention and treatment of occupational voice disorders calls for improved occupational safety and health (OSH) arrangements for voice and speech professionals. On the basis of epidemiological and acoustic-physiological research, the presence of risk to vocal health can be substantiated. From the point of view of the physical load on the vocal apparatus, loading-related physiological changes (adaptation) may play a role in the occupational risk. Environmental factors affect vocal loading changes. In teaching professions, the working environment is shared with children, who benefit from amendments of OSH legislation concerning their teachers.

Normalized amplitude quotient (NAQ) is presented as a method to parametrize the glottal closing phase using two amplitude-domain measurements from waveforms estimated by inverse filtering. In this technique, the ratio between the amplitude of the ac flow and the negative peak amplitude of the flow derivative is first computed using the concept of equivalent rectangular pulse, a hypothetical signal located at the instant of the main excitation of the vocal tract. This ratio is then normalized with respect to the length of the fundamental period. Comparison between NAQ and its counterpart among the conventional time-domain parameters, the closing quotient, shows that the proposed parameter is more robust against distortion such as measurement noise that make the extraction of conventional time-based parameters of the glottal flow problematic. Experiments with breathy, normal, and pressed vowels indicate that NAQ is also able to separate the type of phonation effectively.

In modern societies about one third of the labor force are working in professions in which voice is the primary tool. Voice problems are common in general, but they are even more common in professions in which there is heavy vocal loading, i.e. professions that do not only require prolonged voice use, but also involve extra loading factors such as background noise, long speaking distance, poor room acoustics, lack of adequate equipment like voice amplifiers etc. School and kindergarten teachers can be considered to represent professions with heavy vocal loading. The occupational safety and health arrangements of voice and speech professionals are poorly developed as compared to many other professions. However, the existing legislation could be used to support efforts to improve the working conditions of this large but heterogeneous group.

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Fiberoptic videolaryngoscopy during bicycle ergometry was a well-tolerated and relatively easily established diagnostic tool that could induce dyspnea in more than one half the patients examined. If the symptom of dyspnea appeared, the most frequent diagnosis was exercise- induced vocal cord dysfunction.

To enable the development of appropriate diagnostics and treatment for occupational voice disorders, this study addresses connections between subjective voice complaints and objective observations. The subjects of this study were 24 female customer advisors, who mainly use the telephone during their working hours. During one working day, at four different times, speech samples covering 20 minutes of telephone conversation by the customer service advisors (CSAs) were recorded. In addition, the CSAs filled in a questionnaire (visual analogue scale) concerning their voice problems. To represent the vocal symptoms three variables were used: vocal fatigue, hoarseness and a general sum-variable. A 5-minute sample was taken from recordings for further analyses. This included fundamental frequency, sound pressure level, alpha ratio (the ratio between the spectral energy below and above 1000 Hz) and number of vocal fold vibrations. In the objective acoustic measurements, it was found that fundamental frequency (F0) rose significantly during the working day. Also the self-reported voice symptoms increased significantly during the working day. However, correlations between vocal symptoms and acoustic measures were not found.