Noise abatement in office environments often focuses on the reduction of background speech intelligibility and noise level, as attainable with frequency-specific insulation. However, only limited empirical evidence exists regarding the effects of reducing speech intelligibility on cognitive performance and subjectively perceived disturbance. Three experiments tested the impact of low background speech (35 dB(A)) of both good and poor intelligibility, in comparison to silence and highly intelligible speech not lowered in level (55 dB(A)). The disturbance impact of the latter speech condition on verbal short-term memory (n=20) and mental arithmetic (n=24) was significantly reduced during soft and poorly intelligible speech, but not during soft and highly intelligible speech. No effect of background speech on verbal-logical reasoning performance (n=28) was found. Subjective disturbance ratings, however, were consistent over all three experiments with, for example, soft and poorly intelligible speech rated as the least disturbing speech condition but still disturbing in comparison to silence. It is concluded, therefore, that a combination of objective performance tests and subjective ratings is desirable for the comprehensive evaluation of acoustic office environments and their alterations.

Background sounds, such as narration, music with prominent staccato passages, and office noise impair verbal short-term memory even when these sounds are irrelevant. This irrelevant sound effect (ISE) is evoked by so-called changing-state sounds that are characterized by a distinct temporal structure with varying successive auditory-perceptive tokens. However, because of the absence of an appropriate psychoacoustically based instrumental measure, the disturbing impact of a given speech or nonspeech sound could not be predicted until now, but necessitated behavioral testing. Our database for parametric modeling of the ISE included approximately 40 background sounds (e.g., speech, music, tone sequences, office noise, traffic noise) and corresponding performance data that was collected from 70 behavioral measurements of verbal short-term memory. The hearing sensation fluctuation strength was chosen to model the ISE and describes the percept of fluctuations when listening to slowly modulated sounds (f mod < 20 Hz). On the basis of the fluctuation strength of background sounds, the algorithm estimated behavioral performance data in 63 of 70 cases within the interquartile ranges. In particular, all real-world sounds were modeled adequately, whereas the algorithm overestimated the (non-)disturbance impact of synthetic steady-state sounds that were constituted by a repeated vowel or tone. Implications of the algorithm's strengths and prediction errors are discussed.

With two experiments, effects of irrelevant speech and classroom noise on serial recall of common nouns presented pictorially were investigated in children and adults. Experiment 1 used fixed list lengths for children (first graders) and adults. Experiment 2 used list lengths adjusted to participants' (secondÁthird graders, adults) individual spans. In both experiments, children and adults were equally impaired by irrelevant speech. This contrasts with a related study (differences in methodology) by Elliott (2002), who reported severe increase in the detrimental impact of irrelevant speech with decreasing age. In both experiments, classroom noise had no effect in overall analyses. For Experiment 1, however, separate group analyses revealed impairment in children. Results suggest that effects of irrelevant sounds on serial recall stem from two separate mechanisms: Specific interference due to the sounds' automatic access to short-term memory, and/or attention capture. Only for the latter there is developmental change.

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Continuous noise is played in many open-plan offices to partially mask ambient sounds, in particular background speech. With this, the detrimental impact of background sounds on cognitive performance is intended to be reduced as well as subjectively perceived disturbance. Our experiments explored whether background music can achieve the same effects. Besides collecting subjective rating data, we tested cognitive performance using verbal serial recall. This is the standard task for exploring verbal short-term memory, which is central to human information processing. Either staccato music, legato music or continuous noise was superimposed on office noise. In Experiment 1 (N ¼ 30), only continuous noise reduced the detrimental impact of office noise significantly. Legato music did not qualify in this respect although it did not diminish cognitive performance when presented in isolation in Experiment 2 (N ¼ 20). Subjective ratings in both experiments revealed that most participants would prefer legato music to continuous noise in office environments.

Current literature suggests that wind turbine noise is more annoying than transportation noise. To date, however, it is not known which acoustic characteristics of wind turbines alone, i.e., without effect modifiers such as visibility, are associated with annoyance. The objective of this study was therefore to investigate and compare the short-term noise annoyance reactions to wind turbines and road traffic in controlled laboratory listening tests. A set of acoustic scenarios was created which, combined with the factorial design of the listening tests, allowed separating the individual associations of three acoustic characteristics with annoyance, namely, source type (wind turbine, road traffic), A-weighted sound pressure level, and amplitude modulation (without, periodic, random). Sixty participants rated their annoyance to the sounds. At the same A-weighted sound pressure level, wind turbine noise was found to be associated with higher annoyance than road traffic noise, particularly with amplitude modulation. The increased annoyance to amplitude modulation of wind turbines is not related to its periodicity, but seems to depend on the modulation frequency range. The study discloses a direct link of different acoustic characteristics to annoyance, yet the generalizability to long-term exposure in the field still needs to be verified.

The term irrelevant sound effect (ISE) describes an empirically robust finding in which serial recall performance of visual items is reduced by irrelevant speech. At present little is known about its neurophysiological basis. Although some previous neuroelectric studies have concentrated on responses elicited by irrelevant background sound, whether the processing of visually presented to-be-remembered digits itself is affected by irrelevant speech has yet to be studied. An experiment (n = 20) was conducted in which serial recall performance for visually presented digits was tested during exposure to either irrelevant speech, continuous white noise or silence while measuring EEG activity. White noise was chosen as a control condition, because it constitutes auditory stimulation while leaving serial recall performance unimpaired. In addition to replicating the detrimental behavioural effect of irrelevant speech, an analogous speech-specific early decrease ( approximately 160 ms) in the visual ERP (N1) and subsequently a reduced theta response (4-6 Hz; 400-800 ms) at right prefrontal electrodes were observed. Although irrelevant sound presentation was restricted to the visual presentation phase, power spectra reveal that the weaker theta response for speech persisted in a silent retention phase before serial recall. Based on such data we propose re-evaluating the role attention plays in explaining the ISE.