The effect of hearing protective earmuffs which incorporate active noise reduction (ANR) on sound source identification was studied. The purpose was determine whether ANR interfered with the encoding of cues normally used for directional hearing. Right/left, front/back and within quadrant confusions were assessed in quiet using a circular array of eight loudspeakers. Three stimuli, one-third octave bands centered at 0.5 kHz and 4 kHz and broadband noise, were presented. These enabled an assessment of the utilization of mainly interaural time-of-arrival and level differences, and binaural and spectral cues in combination, respectively. Two groups of normal hearing subjects aged 18-30 and 40-55 years, half male and half female, participated. Overall, age, gender, and ANR were not significant determinants of outcome. The probably of correctly discriminating among the eight speakers decreased significantly with the muffs worn, relative to unoccluded listening by 10%, 35% and 40% for the 0.5 kHz, 4 kHz and broadband stimuli, respectively. The pattern of errors indicated that the earmuffs interfered with the encoding of both binaural (interaural level differences) and spectral cues. With ANR small additional right/left confusions were observed for the low-frequency stimulus (time-of ­arrival cue) for speakers close to the midline axis. The results provide further evidence that earmuffs should not be used in situations where the perception of the direction of hazard is a concern. ANR technology does not appear to increase the handicap.

The objectives in this paper were to analyze noise effects on episodic and semantic memory performance in different age groups, and to see whether age interacted with noise in their effects on memory. Data were taken from three separate previous experiments, that were performed with the same design, procedure and dependent measures with participants from four age groups (13-14, 18-20, 35-45 and 55-65 years). Participants were randomly assigned to one of three conditions: (a) meaningful irrelevant speech, (b) road traffic noise, and (c) quiet. The results showed effects of both noise sources on a majority of the dependent measures, both when taken alone and aggregated according to the nature of the material to be memorized. However, the noise effects for episodic memory tasks were stronger than for semantic memory tasks. Further, in the reading comprehension task, cued recall and recognition were more impaired by meaningful irrelevant speech than by road traffic noise. Contrary to predictions, there was no interaction between noise and age group, indicating that the obtained noise effects were not related to the capacity to perform the task. The results from the three experiments taken together throw more light on the relative effects of road traffic noise and meaningful irrelevant speech on memory performance in different age groups.

Objective: The aim of the present study was to evaluate factors of importance for the experience of temporary threshold shift (TTS), noise- induced tinnitus (NIT), spontaneous tinnitus (ST) in school children. Subjects and Methods: A total of 671 students aged 13-16 years old were asked to fill in a questionnaire containing items concerning TTS, NIT, ST, hearing loss (HL), heredity for HL, noise exposure, history of otitis media, symptoms of anxiety and depression, psychosocial factors and habits, life satisfaction, chronic medical conditions, age, gender and height. The questionnaire was filled in during school hours. Results: Correlations were found with exercise and eating habits, sleep disturbances, BMI, depressive and anxiety disorders, heredity for HL and noise exposure dosage. The risk for TTS was nine times higher in students who reported having a verified hearing loss than in subjects without subjective or verified complaints of hearing loss. The risk for NIT was approximately four times higher in the group who visited concerts 6-12 times per year as compared to those who never attended concerts. There was almost a threefold increase in the risk for ST in the group that sometimes experienced TTS, as compared to those without TTS, and a tenfold increase in risk for ST in those who reported having a verified hearing loss. Conclusion: In school children, exposure to leisure noise is correlated with tinnitus and the risk increases with increasing noise exposure. Sensitivity to subjective hearing loss has similar risk factors as seen for metabolic syndrome and we suggest that this sensitivity may be another side of metabolic syndrome.

The present paper provides the results from two nation-wide telephone surveys conducted in Canada on a representative sample of 5,232 individuals, 15 years of age and older. The goals of this study were to gauge Canadians' annoyance towards environmental noise, identify the source of noise that is viewed as most annoying and quantify annoyance toward this principal noise source according to internationally accepted specifications. The first survey revealed that nearly 8% of Canadians in this age group were either very or extremely bothered, disturbed or annoyed by noise in general and traffic noise was identified as being the most annoying source. A follow-up survey was conducted to further assess Canadians' annoyance towards traffic noise using both a five-item verbal scale and a ten-point numerical scale. It was shown that 6.7% of respondents indicated they were either very or extremely annoyed by traffic noise on the verbal scale. On the numerical scale, where 10 was equivalent to "extremely annoyed" and 0 was equivalent to "not at all annoyed", 5.0% and 9.1% of respondents rated traffic noise as 8 and above and 7 and above, respectively. The national margin of error for these findings is plus or minus 1.9 percentage points, 19 times out of 20. The results are consistent with an approximate value of 7% for the percentage of Canadians, in the age group studied, highly annoyed by road traffic noise (i.e. about 1.8 million people). We found that age, education level and community size had a statistically significant association with noise annoyance ratings in general and annoyance specifically attributed to traffic noise. The use of the International Organization for Standardization/Technical Specification (ISO/TS)-15666 questions for assessing noise annoyance makes it possible to compare our results to other national surveys that have used the same questions.

In this study, two investigations were carried out with adult Long-Evans rats exposed to increasing concentrations of styrene. In the first experiment, the hearing of rats, which were forced to walk in a special wheel during the exposure, was compared to that of rats which were sleepy in their cage. The active rats were exposed to styrene concentrations ranging from 300 to 600 ppm, whereas the sedentary rats were exposed from 500 to 1000 ppm for 4 weeks, 5 days per week, 6 hours per day. In the second experiment, designed to evaluate the hearing risks at threshold limit values, active rats were exposed either to a noise having a Leq8h of 85 dB (equivalent level of a continuous noise for a typical 8-h workday), or to 400-ppm styrene or to a simultaneous exposure to noise and styrene. In both experiments, auditory function was tested by auditory-evoked potentials from the inferior colliculus and completed by morphological analyses of the organ of Corti. The results of the first experiment showed that the same amount of styrene-induced hearing loss can be obtained by using concentrations approximately 200 ppm lower in active rats than in sedentary rats. The second investigation showed that, in spite of the low-intensity noise and the low-concentration of styrene, there is a clear risk of potentiation of styrene-induced hearing loss by noise. These findings and exposure conditions were discussed and extrapolated with regard to the risk assessment for human beings. The authors propose to decrease the French threshold limit value of styrene for ensuring a high level of protection for human hearing.