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- Bengtsson, Johanna, 1974, et al.
(författare)
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Evaluations of effects due to low-frequency noise in a low demanding work situation
- 2004
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 278:1-2, s. 83-99
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Tidskriftsartikel (refereegranskat)abstract
- Noise sources with a dominating content of low frequencies (20-200 Hz) are found in many occupational environments. This study aimed to evaluate effects of moderate levels of low-frequency noise on attention, tiredness and motivation in a low demanding work situation. Two ventilation noises at the same A-weighted sound pressure level of 45 dB were used: one of a low-frequency character and one of a flat frequency character (reference noise). Thirty-eight female subjects worked with six performance tasks for 4 h in the noises in a between-subject design. Most of the tasks were monotonous and routine in character. Subjective reports were collected using questionnaires and cortisol levels were measured in saliva. The major finding in this study was that low-frequency noise negatively influenced performance on two tasks sensitive to reduced attention and on a proof-reading task. Performances of tasks aimed at evaluating motivation were not significantly affected. The difference in work performance was not reflected by the subjective reports. No effect of noise was found on subjective stress or cortisol levels.
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| 3. |
- Bengtsson, Johanna, 1974
(författare)
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Low frequency noise during work. Effects on performance and annoyance
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aims. Low frequency noise (LFN) is defined as "a noise with a dominant frequency content of 20 to 200 Hz". Common sources of LFN in occupational environments are ventilation, heating and air-conditioning systems, computer network installations and compressors. The aims were to evaluate the influence of LFN on performance, annoyance, other subjective effects, cortisol levels and subjective stress. A further aim was to evaluate whether the frequency balance and modulation frequency in a LFN influenced a subject's perception of pleasantness. Methods. All studies were laboratory experiments. The experiment reported in papers I and II comprised 32 subjects who worked for 2 h with four performance tasks under high workload during exposure to LFN and a reference noise at an A-weighted sound pressure level of 40 dB. The experiment reported in paper III comprised 38 subjects who worked for 4 h with six performance tasks under low workload during exposure to LFN or reference noise at an A-weighted sound pressure level of 45 dB. The experiment reported in paper IV comprised 30 subjects who varied the level of the sound characteristic's frequency balance and modulation frequency in the LFN to make the noise more pleasant.Results. LFN impaired performance in tasks with high and moderate demands on cognitive processing when carried out under high workload and in tasks with moderate and low demands when these were performed under low workload. No difference between noise conditions was found in low demand tasks performed under high workload and tasks evaluating motivation performed under low workload. LFN was rated to have a greater impairment on the work capacity and be more annoying than reference noise; the difference between noises was significant under high workload. No difference between noise conditions was found in subjective symptoms, but annoyance and reported impairment of the work capacity due to LFN was related to several symptoms. This was less frequently found for reference noise. Subjects high-sensitive to LFN or to noise in general performed less well and reported higher annoyance due to LFN. The effects caused by LFN were most pronounced for subjects high-sensitive to LFN. Exposure to LFN during high workload resulted in elevated cortisol levels among subjects high-sensitive to noise in general, and a tendency towards the same result was found for subjects high-sensitive to LFN. No clear relationships between cortisol levels and subjective stress were found. The resulting pleasant LFN comprised less perceivable modulations and a lower content of frequencies below 500 Hz. The effect was less marked when the original LFN did not comprise modulations and, when the A-weighted sound pressure level could be altered, a steeper slope was preferred to a higher level. Conclusions. The experiments showed that exposure to LFN during work can impair performance, lead to subjective annoyance and increase cortisol levels, even at moderate sound pressure levels. The effects were influenced by workload and noise sensitivity. The performance effects are hypothesised to be mediated by impaired learning and reduced attention. To achieve a more pleasant LFN, the noise should contain no or little perceivable modulations and a lower relative content of low frequencies.
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| 4. |
- Bengtsson, Johanna, 1974, et al.
(författare)
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Sound characteristics in low frequency noise and their relevance for the perception of pleasantness
- 2004
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Ingår i: Acta Acoustica. ; 90:1, s. 171-180
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Tidskriftsartikel (refereegranskat)abstract
- Noise sources with a dominant content of low frequencies (20-200 Hz) are found in many occupational environments. Work efficiency has been found in two earlier studies to be impaired to a larger degree when working in a low frequency ventilation noise than when working in a flat frequency ventilation noise at the same A-weighted sound pressure level. Other previous studies indicate that different sound characteristics found in low frequency noise are important for the way in which low frequency noise affects humans, and better knowledge of these characteristics could lead to better methods for assessing low frequency noise in occupational environments. The aim of this study was to evaluate the influence of frequency balance between low and high frequencies, which affects the slope of the frequency spectra, and the modulation frequency on subjects´ perception of a pleasant low frequency noise. The results showed that the subjects preferred either a higher or a lower modulation frequency as compared to that of the original low frequency noise, both choices leading to less perceivable modulations. Furthermore, the subjects preferred a lower relative content of frequencies below 500 Hz, but only as long as the original low frequency noise contained modulations and the variations were made within a constant A-weighted sound pressure level. The results are discussed in relation to improved guidelines and to the previously suggested theory of slope of the frequency spectra and problems involved with the implementation of that theory.
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- Bengtsson Ryberg, Johanna, 1974, et al.
(författare)
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Low frequency noise in a paper mill control room
- 2007
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Ingår i: Journal of Low Frequency Noise, Vibration and Active Control. - : SAGE Publications. - 0263-0923 .- 1461-3484 .- 2048-4046. ; 26:3, s. 165-176
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Tidskriftsartikel (refereegranskat)abstract
- This field study aimed to evaluate the prevalence of annoyance and disturbance and the subjective perception of the sound environment due to noise, in an old and a new control room at a large paper mill. Working in a control room requires sustained attention and concentration and, in the case of error messages, rapid and correct decisions. In this study, the personnel's responses were collected by questionnaire, and detailed sound measurements were taken in both control rooms. The A-weighted sound pressure level in the new control room was 54.9 dB, a reduction from the 63.5 dB measured in the old room, and the C-weighted sound pressure level was 66.8 dB, a reduction from the 75.2 dB measured in the old room. The new control room was rated as being a less noisy environment; however, the personnel did complain about noise from other computers/equipment, radios, and the new laboratory.
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| 6. |
- Bengtsson Ryberg, Johanna, 1974, et al.
(författare)
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Low frequency noise in a paper mill control room
- 2004
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Ingår i: The 11th International Meeting on Low Frequency Noise and Vibration and its Control, 2004 30 August-1 September, Maastricht, The Netherlands. ; , s. 15-25
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Konferensbidrag (refereegranskat)
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