Ulf Landström

Health effects of long-term occupational exposure to whole-body vibration: A review

Abstract A review is presented of research on health effects of whole-body vibration on man with the objective of providing a basis for rules and guidelines on exposure to whole-body vibration, particularly for professional drivers. A greater part of the review concerns risks for low-back injuries. After a symmetric review of the literature in the field, the conclusion is drawn that whole-body vibration may contribute to injuries and other problems of the lower back. The exposure-response relationship, however, has not been clarified.

Exposure levels, tonal components, and noise annoyance in working environments

Noise annoyance and noise exposure were analysed in 439 working places. The investigation included different types of working situations and noise with different frequency characteristics. The study included 235 low-frequency environments, 147 middle-frequency environments, and 57 high-frequency environments. The noise annoyance reactions were studied by means of graphical rating scales. The noise was expressed as dBlin, dB(A), dB(B), dB(C), and dB(D). The noise exposures were also classified, based on 13-octave band analysis, into three classes: exposures without tonal components, exposure with one tone, and several tonal components. Classifications were also made with respect to frequency character and exposure levels. The analyses of dose-response relations between annoyance and noise level showed that dB(A) was neither better nor worse than any of the other alternative weighting methods. The correlations between sound level and annoyance ratings were weak. Annoyance was also influenced by other factors than the noise level. People exposed to noise with tonal components were more annoyed than the others. Rated annoyance was further increased when the noise contained several tones. The frequency characteristics and the sound level of the noise affected the strength of the effect of tones on annoyance. The effect of the tonal component on annoyance corresponded to a difference in pressure level of approximately 6 dB.

The effects of broadband, tonal and masked ventilation noise on performance, wakefulness and annoyance

A laboratory study was designed in order to investigate the effects of ventilation noise on performance, fatigue and annoyance. The study was also designed in order to compare the effects of broadband noise 40 dB(A), tonal noise, 40 dB(A), and tonal noise masked by means of low frequency pink noise, 41 dB(A). The study of performance was based on a figure identification test. The annoyance and fatigue were tested by means of rating scales. The analyses of fatigue also included EEG-recordings. The acceptability of the different types of ventilation noise was also analysed through matching tests. The differences in performance between broadband and tonal ventilation noise were significant and did not show any unambiguous tendency. An insignificant tendency of worse performance during broadband exposure and that the tonal ventilation noise should be more tiring could be observed. The tonal exposure was described as less annoying during work. On the other hand, in the matching tests, the subjects tolerated an insignificantly lower level of the tonal ventilation noise compared to the broadband noise. Comparisons between the tonal ventilation noise and the tonal ventilation noise masked by means of a pink noise, showed that the masked ventilation noise was correlated to ambiguous tendencies towards higher performance, lower fatigue but higher annoyance. In the matching tests, the subjects tolerated a lower level of masked ventilation noise compared to the unmasked ventilation noise. Except for the ratings of fatigue, all differences were below the level of significance p 0.05.

Noise and fatigue in working environments

Abstract Laboratory studies carried out in sound chambers give experimental support to the theory that fatigue and wakefulness could be influenced by sound and hearing. The tiring effect is more pronounced during exposure to low frequency noise compared to higher frequencies. A tiring effect was observed at lower levels above the hearing perception curve. As expected, when the sound pressure level was raised or the frequency was increased, stress reactions and alertness was a more frequently occurring effect. The laboratory findings were supported by a field study carried out on lorry drivers. The tiring effect was more pronounced when driving lorries generating higher levels of low-frequency noise compared to lorries generating lower levels.

Noise and annoyance in working environments

Abstract This paper describes a field study of the correlation between annoyance and occupational exposure to noise. Measurements of noise and annoyance were made in different types of working environments with noise dominated by low-frequency, middle-frequency or high-frequency components. The noise was described in terms of dB(A), dB(B), dB(C), dB(D), and dB(lin). Annoyance ratings of the occupational noise and of two verbally described reference noises were collected, using a rating scale. As a result of calibration, a better correlation between noise level and rated annoyance was obtained. The A-weighting procedure did not produce a better prediction of annoyance than any of the other weighting methods.

Acceptable Levels of Tonal and Broad-Band Repetitive and Continuous Sounds during the Performance of Nonauditory Tasks

Three groups of 24 subjects were exposed to a 1000–Hz tone or broad band noise in a sound chamber. During the exposures subjects were engaged in an easy reaction time test or a difficult grammatical reasoning test. For each exposure and work subjects adjusted the noise to a tolerance level defined by its interference with task performance. During the simple reaction-time task significantly higher sound-pressure levels were accepted than during the reasoning test. At the tonal exposure, much lower levels were accepted than during the exposure to broad-band noise. For continuous sound exposures much higher levels were accepted than for noncontinuous exposures. For tonal exposures the difference was approximately 5 dB, for the broad-band exposures approximately 9 dB. In a separate study the effects of the noncontinuity of the noise and pauses were analysed. The raised annoying effect of the noncontinuous noise was not more affected by the noncontinuity of the noise periods than by the noncontinuity of the pauses. The results imply that the annoying reactions to the sound will be increased for repetitive noise and that the reaction is highly influenced by the over-all noncontinuity of the exposure.

ANNOYANCE AND DISCOMFORT DURING EXPOSURE TO HIGH-FREQUENCY NOISE FROM AN ULTRASONIC WASHER

Annoyance and discomfort during exposure to high-frequency noise from an ultrasonic washer have been examined in the experiments carried out with 10 subjects. After a short exposure during which the subjects rated their annoyance and discomfort, a broad-band noise was matched to the ultrasound. The subjects were exposed to three different levels of ultrasound on three different occasions. Analyses showed that ultrasound causes considerable annoyance and discomfort even for the lowest exposure levels. No significant difference between annoyance and discomfort was observed. The matchings indicated, however, that the A-weighting, i.e., the traditional rating technique used for noise evaluations, overestimated the high-frequency sound when evaluating annoyance and discomfort.

Postural Control during and after Exposure to Whole Body Vibrations

The question as to whether the receptor and control systems are activated by a vibratory stimulation depends upon the frequency spectrum, intensity, time of exposure, subjects posture, direction of exposure and body resonances. The purpose of this study is to investigate different exposure directions and exposure frequencies. This has been achieved through analyses of the stabilographic effects during and after exposure to vibration

Noise in the office: Part II – The scientific basis (knowledge base) for the guide

Noise is one of the most widespread environmental problems in workplaces, including offices. Dissatisfaction with the noise conditions may have a considerable impact on the general satisfaction with the job and the working environment. Generally, the noise levels emitted from individual machines installed in offices have been lowered compared to the situation in the past. However, this development has not led to any appreciable reduction of the total noise level in offices. The noise emitted from sources installed in the building is another great problem in many office environments. Ventilation noise has been an increasing problem in the past decade due to a notable lack of insight into noise problems among the installers of ventilation systems. Disturbance from outdoor noise sources is another example of noise problems in offices, which depend on remarkable shortcomings of the building technique. This chapter also discusses two types of noise effects found in offices. These effects include subjective responses (annoyance, disturbance) and behavioral effects (primarily performance effects).