The contradictory and confusing results in noise research on humans may partly be due to individual differences between the subjects participating in different studies. This review is based on a twelve year research on the role of neuroticism, extroversion and subjective noise sensitivity during mental work in noisy environment. Neurotic persons might show enhanced "arousability" i.e. their arousal level increases more in stress. Additional unfavorable factors for neurotics are worrying and anxiety, which might prevent them coping successfully with noise, or some other stressors during mental performance. In numerous experiments introverts have showed higher sensitivity to noise during mental performance compared to extroverts, while extroverts often cope with a boring task even by requesting short periods of noise during performance. Correlation analyses have regularly revealed a highly significant negative relation between extroversion and noise annoyance during mental processing. Numerous studies have shown that people with high noise sensitivity may be prevented from achieving the same work results as other people in noisy environment, thus leading to psycho­somatic, neurotic or other difficulties. Positive relation between noise annoyance and subjective noise sensitivity might be very strong. Our results have shown, after matching with the results of other relevant studies, that more stable personality, with extroversive tendencies and with a relatively lower subjective noise sensitivity measured with standard questionnaires, may be expected to better adapt to noise during mental performance, compared to people with opposite personality traits.

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A total of twenty-five subjects were cloistered for a period of 70 hours, five at a time, in a hyperbaric chamber modified to simulate the conditions aboard the International Space Station (ISS). A recording of 72 dBA background noise from the ISS service module was used to simulate noise conditions on the ISS. Two groups experienced the background noise throughout the experiment, two other groups experienced the noise only during the day, and one control group was cloistered in a quiet environment. All subjects completed a battery of cognitive tests nine times throughout the experiment. The data showed little or no effect of noise on reasoning, perceptual decision-making, memory, vigilance, mood, or subjective indices of fatigue. Our results suggest that the level of noise on the space station should not affect cognitive performance, at least over a period of several days.

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Speech warnings and communication systems are increasingly used in noisy, high workload environments. An important decision in the development of such systems is the choice of a male or a female speaker. There is little objective evidence to support this decision, although there are many misconceptions and misunderstandings on this topic. This paper suggests that both acoustic and non-acoustic differences (such as social attributions towards speakers of different sexes) between male and female speakers is negligible, therefore the choice of speaker should depend on the overlap of noise and speech spectra. Female voices do however appear to have an advantage in that they can portray a greater range of urgencies because of their usually higher pitch and pitch range. An experiment is reported showing that knowledge about the sex of a speaker has no effect on judgements of perceived urgency, with acoustic variables accounting for such differences.

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Critical to survival, and also to the organism's efficient management of the flow of information in the brain, is attentional selectivity; the ability to select one source of information to guide action whilst ignoring others that are irrelevant to the current behavioural goal. But such selectivity is not merely the inclusion of the relevant information and the complete neglect of irrelevant information. We discuss in this paper the way that all sound is processed in an obligatory fashion - whether relevant or irrelevant - and discuss the fate of sound in the case when it is irrelevant to the immediate mental task. Using the so-called irrelevant sound paradigm we show that unattended information is both registered and organised. This obligatory process of organisation compromises the efficiency of particular types of mental activity. We discuss how such interference comes about but the key emphasis is upon the possible beneficial effects of such processing-of-the-irrelevant, in allowing the switching of attention to be more facile and intelligent and in allowing the accumulation of evidence about statistical regularities in the auditory world (such as those helpful to the efficient perception, acquisition and use of language). In sum, we describe how purposeful processing based on directed attention is in a state of tension with the obligatory, automatic processing of the unattended. One of the consequences of this tension is typically manifested in auditory distraction, but the benefits of processing of the attended may considerably outweigh this disadvantage.

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Many jobs at the Department of Fisheries and Oceans Canada (DFO) have several features in common: they are often performed in noisy environments and involve a number of auditory skills and abilities, such as speech communication, sound localization, and sound detection. If an individual lacks these skills and abilities, it may constitute a safety risk for this individual, as well as for fellow workers and the general public. A number of scientific models have been developed to predict performance on these auditory skills based on diagnostic measures of hearing such as pure-tone audiograms. While these models have significant scientific and research value, they are unable to provide accurate predictions of real life performance on auditory skills necessary to perform hearing-critical jobs. An alternative and more accurate approach has been developed in this research project. A direct measure of functional speech perception in noise (Hearing in Noise Test: HINT) has been identified and validated for use in screening applicants for hearing-critical jobs in DFO. This screening tool has adequate and well-defined psychometric properties (e.g. reliability, sensitivity, and validity) so that screening test results can be used to predict an individual's ability to perform critical auditory skills in noisy environments, with a known degree of prediction error. Important issues must be considered when setting screening criteria. First, the concept of hearing-critical tasks must be reviewed, since these tasks are often performed in high noise levels where normally-hearing people cannot hear adequately. Second, noise-induced hearing loss is frequent in these noisy environments, and workers who acquire a hearing loss might not continue to meet the minimal auditory screening criteria throughout their career. Other senses (e.g., vision, touch) also play an important role in these environments. Third, adaptation strategies have to be considered when recruits or incumbents fail the screening test.

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Usually the perception of acoustic signals is investigated under conditions where the subjects pay full attention to the signals. It can be assumed that the threshold of signal perception is much higher if the attention has simultaneously to be focused on the execution of any kind of other activity. In the following experiment subjects have to perceive acoustic signals while solving different arithmetical tasks at the same time. The results (number of perceived signals, number of arithmetical tasks solved, reaction time, and solving time) show that the threshold of signal perception rises while other tasks are being performed simultaneously. Consequences for the recognition of warning signals in occupational safety and in traffic conditions are discussed.

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