Sabine Schlittmeier

The impact of background speech varying in intelligibility: Effects on cognitive performance and perceived disturbance.

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.

Does irrelevant music cause an irrelevant sound effect for auditory items

The irrelevant sound effect (ISE) describes the significant reduction in verbal serial recall during irrelevant sounds with distinct temporal-spectral variations (changing-state sound). Whereas the ISE is well-documented for the serial recall of visual items accompanied by irrelevant speech and nonspeech sounds, an ISE caused by nonspeech sounds has not been reported for auditory items. Closing this empirical gap, Experiment 1 (n=90) verified that instrumental staccato-music reduces auditory serial recall compared to legato-music and silence. Its detrimental impact was not due to perceptual masking, disturbed encoding, or increased listening effort, as the employed experimental design and methods ensured. The found nonspeech ISE in auditory serial recall is corroborated by Experiment 1b (n=60), which, by using the same experimental design and methods, replicated the well-known ISE during irrelevant changing-state speech compared to steady-state speech, pink noise, and silence.

Combined effects of acoustic and visual distraction on cognitive performance and well-being

Information work is usually performed in offices and influenced by the combined effects of acoustics, room climate, lighting and air quality. However, the principal part of literature solely focuses on the individual effects of physical parameters. This study (n = 32) investigates the combined effects of acoustic and visual distraction with regard to cognitive performance and well-being. Therefore low level background speech (40 dB(A)) of good or poor intelligibility was combined with either static or dynamic lighting. Experimental testing lasted for approx. 7 h for each participant and was conducted in mock-up offices. No interaction effects of background speech and lighting conditions with regard to cognitive performance were found. However, the results prove that even low level background speech of high intelligibility significantly impairs short-term memory, reasoning ability and well-being. But no effect of background speech on text comprehension and sustained attention was found. Visual distraction due to dynamic lighting caused significant complaints but did not impair performance. An interaction effect of background speech and lighting conditions was found with regard to perceived performance during task processing. Test persons only felt to perform better, if background speech of low intelligibility was combined with static lighting. It is shown that the effects on cognitive performance and well-being must be considered separately since these effects are rarely consistent.

Can the irrelevant speech effect turn into a stimulus suffix effect

The irrelevant sound effect (ISE) and the stimulus suffix effect (SSE) are two qualitatively different phenomena, although in both paradigms irrelevant auditory material is played while a verbal serial recall task is being performed. Jones, Macken, and Nicholls (2004) have proposed the effect of irrelevant speech on auditory serial recall to switch from an ISE to an SSE mechanism, if the auditory-perceptive similarity of relevant and irrelevant material is maximized. The experiment reported here (n = 36) tested this hypothesis by exploring auditory serial recall performance both under irrelevant speech and under speech suffix conditions. These speech materials were spoken either by the same voice as the auditory items to be recalled or by a different voice. The experimental conditions were such that the likelihood of obtaining an SSE was maximized. The results, however, show that irrelevant speech—in contrast to speech suffixes—affects auditory serial recall independently of its perceptive similarity to the items to be recalled and thus in terms of an ISE mechanism that crucially extends to recency. The ISE thus cannot turn into an SSE.

Unmasking the effects of masking on performance: The potential of multiple-voice masking in the office environment

Broadband noise is often used as a masking sound to combat the negative consequences of background speech on performance in open-plan offices. As office workers generally dislike broadband noise, it is important to find alternatives that are more appreciated while being at least not less effective. The purpose of experiment 1 was to compare broadband noise with two alternatives-multiple voices and water waves-in the context of a serial short-term memory task. A single voice impaired memory in comparison with silence, but when the single voice was masked with multiple voices, performance was on level with silence. Experiment 2 explored the benefits of multiple-voice masking in more detail (by comparing one voice, three voices, five voices, and seven voices) in the context of word processed writing (arguably a more office-relevant task). Performance (i.e., writing fluency) increased linearly from worst performance in the one-voice condition to best performance in the seven-voice condition. Psychological mechanisms underpinning these effects are discussed.

The effects of intelligible irrelevant background speech in offices – cognitive disturbance, annoyance, and solutions

Purpose – This paper aims to give an overview on four empirical studies which explored the impact of background speech on cognitive performance and subjectively perceived disturbance. Background speech is the most serious noise problem in shared-room and open-plan offices for employees who are supposed to do silent, concentrated work. Different measures of acoustic office optimization, as well as the outstanding role of the intelligibility of background speech for its disturbance impact, are empirically evaluated. Design/methodology/approach – The article provides a synopsis describing the core empirical results of four of our empirical studies. A survey study among office employees (n = 659) explored the subjective importance of office acoustics. Three experimental studies (n1 = 20; n2 = 30; n3 = 24) evaluated the effects of reduced background speech level, play-back of partial maskers and reduced speech intelligibility on cognitive performance and subjective ratings. Findings – Background speech is subj...

The impact of road traffic noise on cognitive performance in attention-based tasks depends on noise level even within moderate-level ranges

Little empirical evidence is available regarding the effects of road traffic noise on cognitive performance in adults, although traffic noise can be heard at many offices and home office workplaces. Our study tested the impact of road traffic noise at different levels (50 dB(A), 60 dB(A), 70 dB(A)) on performance in three tasks that differed with respect to their dependency on attentional and storage functions, as follows: The Stroop task, in which performance relied predominantly on attentional functions (e.g., inhibition of automated responses; Experiment 1: n = 24); a non-automated multistage mental arithmetic task calling for both attentional and storage functions (Exp. 2: n = 18); and verbal serial recall, which placed a burden predominantly on storage functions (Experiment 3: n = 18). Better performance was observed during moderate road traffic noise at 50 dB(A) compared to loud traffic noise at 70 dB(A) in attention-based tasks (Experiments 1-2). This contrasted with the effects of irrelevant speech (60 dB(A)), which was included in the experiments as a well-explored and common noise source in office settings. A disturbance impact of background speech was only given in the two tasks that called for storage functions (Experiments 2-3). In addition to the performance data, subjective annoyance ratings were collected. Consistent with the level effect of road traffic noise found in the performance data, a moderate road traffic noise at 50 dB(A) was perceived as significantly less annoying than a loud road traffic noise at 70 dB(A), which was found, however, independently of the task at hand. Furthermore, the background sound condition with the highest detrimental performance effect in a task was also rated as most annoying in this task, i.e., traffic noise at 70 dB(A) in the Stroop task, and background speech in the mental arithmetic and serial recall tasks.

What characterizes changing‐state speech in affecting short‐term memory? An EEG study on the irrelevant sound effect

The irrelevant sound effect (ISE) describes reduced verbal short-term memory during irrelevant changing-state sounds which consist of different and distinct auditory tokens. Steady-state sounds lack such changing-state features and do not impair performance. An EEG experiment (N=16) explored the distinguishing neurophysiological aspects of detrimental changing-state speech (3-token sequence) compared to ineffective steady-state speech (1-token sequence) on serial recall performance. We analyzed evoked and induced activity related to the memory items as well as spectral activity during the retention phase. The main finding is that the behavioral sound effect was exclusively reflected by attenuated token-induced gamma activation most pronounced between 50-60 Hz and 50-100 ms post-stimulus onset. Changing-state speech seems to disrupt a behaviorally relevant ongoing process during target presentation (e.g., the serial binding of the items).

Short-term annoyance reactions to stationary and time-varying wind turbine and road traffic noise: A laboratory studya)

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 effects of spectral and temporal parameters on perceived confirmation of an auditory non-speech signal

In human-machine interactions, the confirmation of an action or input is a very important information for users. A paired comparison experiment explored the effects of four acoustic parameters on the perceived confirmation of auditory non-speech signals. Reducing the frequency-ratio and the pulse-to-pulse time between two successive pulses increased perceived confirmation. The effects of the parameters frequency and number of pulses were not clear-cut. The results provide information for designing auditory confirmation signals. It is shown that findings about the effects of certain parameters on the perceived urgency of warning signals cannot be easily inverted to perceived confirmation.