| 3. |
- Jahncke, Helena
(författare)
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Cognitive performance and restoration in open-plan office noise
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation presents four experimental studies (in four papers) with the overall aim to investigate the effects of office noise on cognitive performance and restoration. In the first two papers the focus was on the effects of different sound levels (i.e., the mean level from all sound sources at an office, such as speech, phones, people walking) on performance, fatigue and stress. In the last two papers the focus was on the effects of background speech, as this has previously been shown to be the most disturbing noise source in open-plan offices. Paper I demonstrated decreased word memory performance, increased fatigue and motivational deficits when the background sound level increased by 12 dB, from 39 to 51 dB LAeq. Paper II showed that the sound level effects were more pronounced for individuals with a hearing impairment. Unexpectedly, no effects were found of acute noise exposure on the participant´s stress hormone levels (Paper I and Paper II).Regarding effects of irrelevant speech, Paper III showed that cognitive performance decreased as a function of background speech intelligibility, the higher the intelligibility depicted by the Speech Transmission Index (STI), the worse the performance. The results indicated that the STI-value must be less than 0.50, to avoid a negative influence on performance. Further, both Paper III and IV showed that performance is more impaired by background speech if the focal task requires episodic memory and rehearsal—such as word memory and information search. Interestingly, some tasks were insensitive for speech.The restorative effects of a break were addressed in Paper I and II (i.e., directly after the work sessions in noise). The break period differed in content between the participants. Paper I showed that a break with a nature movie with corresponding sound increased energy ratings compared to just listening to river sounds or office noise. Continued exposure to office noise gave the lowest ratings of motivation after the break. Paper II showed improved arithmetic performance and motivation after the break with a nature movie and decreased performance and motivation after continued noise exposure. For the hearing impaired participants, however, continued noise during the break increased motivation and performance, while the movie did not.Taken together, the current thesis demonstrates that open-plan office noise can have a negative impact on fatigue, motivation and performance. How much performance is impaired varies with the cognitive processes required by the tasks performed and hearing status. Moreover, continued noise exposure during a short break can further decrease motivation and subsequent performance.
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| 4. |
- Ljung, Robert
(författare)
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Room acoustics and cognitive load when listening to speech
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis investigated the effects of background noise or a long reverberation time in learning situations. All studies used spoken texts that were presented above the speech intelligibility threshold, but were degraded enough to make listening more effortful. The basic hypothesis for the whole project was that listening to speech in a bad acoustic environment should increase the cognitive load for the listener, which should impair memory of the text. In Paper I the auditory stimuli were lists of words and sentences that were degraded by a background noise. Paper II was a replication of the experiment from paper I, but the independent variable was changed from the level of the background noise to reverberation time. Paper III included two experiments where the stimulus material was 10 minutes lectures.Paper IV included two studies. The first experiment investigated whether serial recall performance is affected when words are presented in long reverberation time (Exp 1a). In experiment 1b word lists were presented in long or short reverberation time or with a background noise. The stimuli were recorded in one classroom with extremely good and one with very bad acoustic design. In experiment 2 word lists with many or few phonological neighbours were presented with long or short reverberation time. In all studies some measure of working memory capacity was included. Taken together, the overall results could be summarized in two sentences: Hearing what is said is a necessary but not a sufficient criterion for people to remember what is said, which means that spoken information should be heard without special effort, otherwise proper learning is jeopardized. No consistent relation was found between working memory capacity and the learning effect in the unfavorable listening conditions.
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