Fredric Lindström

Observations of the Relationship Between Noise Exposure and Preschool Teacher Voice Usage in Day-Care Center Environments

Although the relationship between noise exposure and vocal behavior (the Lombard effect) is well established, actual vocal behavior in the workplace is still relatively unexamined. The first purpose of this study was to investigate correlations between noise level and both voice level and voice average fundamental frequency (F₀) for a population of preschool teachers in their normal workplace. The second purpose was to study the vocal behavior of each teacher to investigate whether individual vocal behaviors or certain patterns could be identified. Voice and noise data were obtained for female preschool teachers (n=13) in their workplace, using wearable measurement equipment. Correlations between noise level and voice level, and between voice level and F₀, were calculated for each participant and ranged from 0.07 to 0.87 for voice level and from 0.11 to 0.78 for F₀. The large spread of the correlation coefficients indicates that the teachers react individually to the noise exposure. For example, some teachers increase their voice-to-noise level ratio when the noise is reduced, whereas others do not.

Mean F0 Values Obtained Through Standard Phrase Pronunciation Compared With Values Obtained From the Normal Work Environment: A Study on Teacher and Child Voices Performed in a Preschool Environment

Mean fundamental frequency (F(0)) values are often used in research on vocal load. In this study, we examine how the mean F(0) differs when evaluated through pronouncing a standard phrase as compared to the mean F(0) obtained in a real work/play environment. We also examine how the F(0) values change throughout the day. The study was performed in a preschool, nine adult female preschool teachers and 11 children participated. The participants wore a digital recorder equipped with an accelerometer, which was attached to the neck. In the study, the participant first pronounced a standard phrase in a controlled environment; thereafter, the voice was recorded in the environment where both children and adults normally reside throughout the day, denoted by the work/play environment. For each participant, the procedure was repeated four times throughout the day. Analyses showed that the F(0) values of the childrens and adults voices were significantly higher when recorded in the work/play environment as compared to the controlled environment. The average difference was 36 Hz for adults and 24 Hz for children. Previous studies have shown an increase of F(0) over the day for teachers. In this study, an increase between morning and afternoon values was found amounting to 8 Hz for adults and 24 Hz for children. For the child population, this increase was statistically significant. However, the total changes over the day revealed a somewhat more complex scheme, with an increase of F(0) in the morning, a decrease during lunch, and finally an increase in the afternoon. This pattern was verified statistically for the joint child-adult population.

A comparison of two active‐speaker‐detection methods suitable for usage in noise dosimeter measurements

Measuring noise exposure in a working environment is often done by using standard noise dosimeters. This method is suitable for the evaluation of many working environments. However, in some situations the worker uses his/her voice a large amount during the day, e.g. teachers in a preschool environment. Thus, in these situations regular dosimeter measurements will not correspond to the actual noise exposure. In order to provide correct measurements, methods that can detect when the workers own voice is active are required. This paper presents a study of two such methods originating from voice research; the binaural and the throat microphone methods. The methods are compared using a receiver operating characteristics based method, where the performance is assessed by the Probability‐of‐failure measure, i.e. the percentage of own voice that the method failures to detect correctly. The evaluation is performed in a lab environment as well as in real field conditions in a preschool. The results of the study show that both methods can be successful in a controlled low noise ( 6%).