Hearing threshold and heart rate in men after repeated exposure to dynamic muscle work,sinusoidal vs stochastic whole body vibration and stable broadband noise

Summary Changes in the temporary hearing threshold (TTS₂) and heart rate (HR) were examined in subjects exposed to stable noise, whole body vibration and dynamic muscular work at a dry-bulb temperature of 30°C. The exposure combinations consisted of three categories of dynamic muscular work with varying loads (2 W, 4 W, 8 W), of two categories of noise and of three categories of vibration. The noise categories were: (1) no noise, and (2) stable, broadband (bandwidth 0.2-16.0 kHz) A-weighted noise with an intensity of 90 dB. The vibration categories were: (1) no vibration, (2) sinusoidal whole body vibration (Z-axis) with a frequency of 5 Hz, and (3) stochastic broadband (bandwidth 2.8–11.2 Hz) whole body vibration. A single test consisted of a control period of 30 min, three consecutive exposure periods of 16 min, each followed by a 4-min post-exposure interval and a recovery period of 15 min. The results of the variance analyses indicated that noise had the most notable effect on the TTS₂ values at the hearing frequencies of both 4 and 6 kHz. Of the paired combinations, noise plus vibration and noise plus dynamic muscular work caused the most obvious combined effects. The combined effect of all three factors (noise, vibration and work) on the TTS₂ values after three consecutive exposure periods was significant at the 2.5% level at the 4 kHz hearing frequency and at the 5% level at the 6 kHz hearing frequency. The added effect of vibration on enhanced TTS₂ values was particularly clear when the vibration was stochastic and when the subjects had a low (2 W) working efficiency. Increasing the working efficiency, on the other hand, seemed to retard increases in the hearing threshold. Thus TTS₂ values seemed to reflect the changes in HR values. It is as if the low rate of cardiovascular activity during light dynamic muscular work had enabled the manifestation of the cardiovascular effects of noise and vibration; during strenuous dynamic muscular work, however, the high rate of cardiovascular activity aimed in some way at compensating for the effects of noise and vibration on blood circulation.A brief account of some of the results from the audiometric measurements has been given in San Francisco at the eleventh Inter-Noise Conference in May 17 to 19, 1982     

Studies of combined effects of sinusoidal whole body vibrations and noise of varying bandwidths and intensities on TTS2 in men

Summary This study analyses the data from three laboratory experiments concerning the separate and combined effects on temporary threshold shifts in hearing (TTS2) of sinusoidal low-frequency (5 Hz — 2.12 m/s² and 10 Hz —2.65 m/s²), whole body vibration (along the Z-axis), and continuous (white) noise with eight different bandwidths and intensity levels of 85 dB(A), 90 dB(A) and 98 dB(A). Altogether 370 separate personal experiments were performed using a one-man exposure chamber system. A single experiment consisted of a 30-min pre-exposure period, three 16-min exposure periods, and a 15-min post-exposure period. The data suggested that the TTS₂ induced by noise was increased by vibration. Actually, vibration at a frequency of 5 Hz and noise with bandwidths of 1–4 kHz, 1–8 kHz or 0.2–16 kHz comprised the most significant exposure combinations. After such exposures, the increase in TTS₂ values was defined most clearly for 4 kHz and 6 kHz test frequencies. The increase of thresholds was most marked during the first 16-min exposure period, even though most TTS₂ values determined after the third consecutive exposure period were higher than after the first and second exposures. Figures obtained after the third exposure period proved that exposure to simultaneous vibration and broad band noise (i.e. noise with a bandwidth of 0.2–16 kHz) increased TTS₂ values 1.2–1.5 times more in the 4 kHz audio range than such a broad band noise alone. No single vibration condition induced the same amount of TTS₂.     

Cardiovascular changes and hearing threshold shifts in men under complex exposures to noise,whole body vibrations,temperatures and competition-type psychic load

Summary This study deals with changes in the temporary hearing threshold (TTS₂), heart rate (HR), R-wave amplitude (RWA), diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure (PP) and reaction time (RT) in subjects (n = 108) who, while working on a choice reaction apparatus, were exposed in an exposure chamber to combinations of noise and vibration at dry bulb temperatures of 20° and 30° C. The study was carried out as a type 2-3-3 factorial experiment, the number of the exposure combinations thus being 18. To find out the effects of competition-type psychic stress, some of the subjects were placed in a competitive group and some in a non-competitive group. The members of the competitive group were given financial encouragement and information on their progress during the test, whereas those in the non-competitive group worked at the rate they considered best without any monetary rewards or interim information. The noise classes were: (1) no noise, (2) a stable broadband (bandwidth 0.2–16.0 kHz) A-weighted noise of 90 dB not related to competition, and (3) a stable broadband A-weighted noise of 90 dB related to competition about the fastest reaction time. The vibration classes were: (1) no vibration, (2) sinusoidal whole body vibration (Z-axis) at a frequency of 5 Hz, and (3) stochastic broadband (bandwidth 2.8–11.2 Hz) whole body vibration (Zis). The acceleration (rms) of both vibrations was 2.12m/s². One experiment consisted of a control period of 30 min, three consecutive exposure periods of 16 min with an interval of 4 min, and a 15-min recovery period. The variance analysis model best explained the variation in TTS₂ values at 4 kHz and second best the variation in TTS₂ values at 6 kHz; it explained the variation in HR values third best, the variation in SBP values fourth best and the variation in PP values fifth best. On the other hand, the model explained least well the variation in DBP and RWA values. In general, the explanatory power of the model increased together with the number of exposures. The psychic stress caused by competition accelerated the growth of the TTS₂ values, HR values and SBP values, when the subjects were simultaneously exposed to noise or to a combination of noise and vibration. An interesting finding for the continuation of the research project was that sinusoidal and stochastic vibration affected the cardiovascular changes, temporary hearing threshold and reaction times in different ways.Some preliminary results from the cardiovascular measurements were presented in Moscow at the International Soviet-American Conference in memory of PK Anokhin, Emotions and behavior: a systems approach, 27–29 June, 1984     

Single and joint actions of noise and sinusoidal whole body vibration on TTS2 values and low frequency upright posture sway in men

Summary In the present study the changes in the TTS₂ values and body upright posture sway were examined after exposure of subjects (n =10) to stable broadband (white) noise (90 dB) alone, to sinusoidal vibration alone [directed vertically at the whole body (Z axis)], and to simultaneous exposure combinations of noise and vibrations of the same type. The frequency of the vibration was 5 Hz, but its acceleration was either 2.12 or 2.44 m/s². There were six exposure combinations, and subsequently 60 tests were carried out in an exposure chamber. One test consisted of a control period of 30 min, of three consecutive exposure periods of 16 min each and of a recovery period of 15 min. After the three exposure combinations which included noise, half of the subjects were exposed to vibration during the recovery period. Apart from indicating an increase in the temporary hearing threshold, the results showed that simultaneous exposure to noise and vibration increases the instability of the body upright posture. The TTS₂ values at the 4 and 6 kHz frequencies increased considerably more rapidly when the subjects were exposed simultaneously to noise and vibration than when exposed to noise alone. Without exception, the TTS₂ values increased most during the first exposure period. It was noteworthy that exposure to vibration during the recovery period accelerated the recursion of the TTS₂ values, especially in cases where the subjects had been exposed to noise alone. The variance of the body sway amplitudes and the standard deviation increased within the frequency range 0.063\2-2.000 Hz owing to noise alone and simultaneous noise and vibration. In the directions X and Y, within the frequency ranges 0.063\2-0.100 Hz and 0.100\2-0.600 Hz, the means of the maximum amplitudes of body sway increased especially in connection with those tests in which the subjects had been simultaneously exposed to noise and vibration.Preliminary results from the stabilometric measurements were presented in Espoo, Finland, at the International Course on Occupational Safety Research on November 1 to 5, 1982     

Bioresponses in men after repeated exposures to single and simultaneous sinusoidal or stochastic whole body vibrations of varying bandwidths and noise

Summary This study deals with the changes in temporary hearing threshold (TTS₂), upright body posture sway amplitudes in the X and Y direction, heart rate (HR), R-wave amplitude (RWA), systolic (SBP) and diastolic (DBP) blood pressure, pulse pressure (PP) and the index characterizing haemodynamic activity (HDI), when the subjects were exposed to noise alone, to vibrations alone or to simultaneous noise and vibrations. The experiments were carried out in an exposure chamber and the number of exposure combinations was 12. Seven healthy, male students volunteered as subjects, making a total number of 84 experiments. For each person the experiment consisted of a 30-min control period, five consecutive 16-min exposures, between which there was a 4-min measuring interval, and a 15-min recovery period. The noise was broadband (bandwidth 0.2–16.0 kHz) A-weighted (white) noise. The noise categories were: (1) no noise and (2) noise with an intensity of 90 dBA. The categories of low-frequency whole body vibration in the direction of the Z-axis were: (1) vibration within the range 4.4–5.6 Hz, (2) vibration within the range 2.8–5.6 Hz, (3) vibration within the range 2.8–11.2 Hz, (4) vibration within the range 1.4–11.2 Hz and (5) sinusoidal vibration with a frequency of 5 Hz. The (rms) acceleration in all the vibration models was 2.12 m/s². The results showed that the (TTS₂), values at 4 and 6 kHz increased as a result of simultaneous exposure to noise and vibration significantly more than as a result of exposure to noise alone. The (TTS₂), values increased more intensely during the first 16-min exposure. The means of the variances in the amplitudes of body upright posture sway changed not only after exposures to vibration alone, but also after exposure to noise alone. The means of the sway variances in the X and Y directions at 0.1 Hz and within the range 0.06 to 2.00 Hz increased only when the vibration in the noise-vibration combination was sinusoidal. The changes in the heart rate, R-wave amplitude and blood pressure values also depended on the bandwidth of the vibration, the number of consecutive exposures and on whether the subjects were simultaneously exposed to noise in addition to vibration. As a rule, the effects of sinusoidal vibration differed from those due to stochastic vibrations.Some preliminary results from measurements were presented in Moscow at the International Working Meeting Criteria of evaluation of the effects of whole-body vibration on a man, 12–16 March, 1984.     

Dependency of temporary threshold shift of vibratory sensation in fingertip on 1/3 octave-band hand-arm vibration exposure period

Objectives  To investigate the dependency of temporary threshold shift of vibratoty sensation (TTS_v) in fingertip on hand-arm vibration exposure period. Methods  Six healthy students were instructed to grip a vibrating or nonvibrating handle in the experimental room. The gripping force was 40 N. The vibratory sensation threshold at 125 Hz was measured before and after the exposure in the exposed middle fingertip. The exposure vibration was vertical and the 1/3 octave-band vibration with had a central frequency of 200 Hz and an intensity of 39.2 m/s². The exposure periods were 8, 15, 30, 60, 120, 240 and 600 s. TTS_v,t was evaluated as the difference in vibratory sensation threshold between immediately before and t seconds after the exposure. Results  TTS_v recovered exponentially as in several previous studies and its use enabled us to estimate the time constant and TTS_v,0. TTS_v,0 with vibration exposure was significantly larger than that without it. The regression analysis of the relationship between vibration exposure period (T) and TTS_v,0 (T) for each subject confirmed the good fit of the equation TTS_v,0(T)=B₀+B₁ ^*Log₁₀(T), where B₀ and B₁ are the calculated constants (adjusted R²=0.56–0.87). The time constants did not show such a clear dose effect relationship of exposure period as TTS_v,0. Conclusion  The dependency of TTS_v,0 on vibration exposure period was asymptotically proportional to the logarithm of gripping period. To more quantitatively confirm the relationship of the time constants for recovering time course of TTS_v, it may be necessary to improve the measurement method for TTS_v.     

Application of a new,self-recording,vibratory sensation meter to measure temporary threshold shift of vibratory sensation caused by local vibration exposure

A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTS_v) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSV_v,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (t_c) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The t_c corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTS_v. These parameters enable us to examine more generally the relationships of TTS_v to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTS_v,0 and t_c were used to examine the dependency of TTS_v on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTS_v,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTS_v,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.     

The temporary threshold shift of vibratory sensation induced by composite-band vibration exposure

Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTS_{v, 0}) induced by 1/3 octave-band vibration. We then measured TTS_v after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTS_{v, 0} on the basis of the above relationship. The TTS_{v, 0} induced by the composite vibration was not larger than the TTS_{v, 0} induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTS_{v, 0} determines the TTS_{v, 0} by broad-band random vibration.     

Temporary threshold shift of vibratory sensation induced by a vibrating handle and its gripping force

•Objective This study examines the effect of the force with which a vibrating handle is gripped on the temporary threshold shift of vibratory sensation (TTS_v) induced by hand-arm vibration. •Methods Six healthy subjects gripped a handle vibrating with a 1/3 octaveband vibration, with a central frequency of 200 Hz and an intensity of 39.2 m/s². Exposure was for 1 min and 10 min, respectively. Gripping forces for the 1-min exposure were 5 N, 10 N, 40 N and 80 N, respectively, with 0 N push-pull force. Gripping forces for the 10-min exposure were the same as for the 1-min exposure, but omitting 80 N. The vibratory sensation threshold at 125 Hz was measured before and after exposure of an exposed fingertip to vibration. The differences measured determine TTS_v,t at timet. TTS_v,t determines TTS_v,0, that is, the temporary threshold shift of vibratory sensation immediately after exposure to vibration according to the estimate made on the basis of the preceding study. The same experimental conditions were repeated 3 times on different days in a soundproof and thermoregulated room. •Results Our findings show that TTS_v increases significantly with increasing gripping force. We also determined the quantitative relationships between TTS_v,0 and gripping force as described by the equation wherek _f andc _f are constants andF is gripping force. •Conclusion This study revealed the importance of ergonomic design in reducing the force with which a vibrating handle is gripped to prevent an adverse effect of local vibration. The equation devised may help in the quantitative assessment of the effect of reduced gripping force.     

Combined effects of hand-arm vibration and noise on temporary threshold shifts of hearing in healthy subjects

 Object: To investigate whether hand-arm vibration and noise have a combined effect on temporary threshold shift (TTS) of hearing among healthy subjects. Method and design: Nineteen healthy subjects with an average age of 25.7 (SD 7.7) years were exposed to vibration (30 m/s², 60 Hz), noise [90 dB(A)] and both, respectively. The subject’s right hand was placed on the plate of a vibrator and the right ear exposed to noise via headphones. Subjects were exposed to vibration and/or noise for 3 min and after a 1-min pause the exposure was repeated five times. Hearing thresholds at 1, 4 and 6 kHz were measured during the time periods before, between (during pauses) and after exposure. Results: Exposure to vibration alone caused almost no hearing threshold changes at every frequency tested. But exposure to noise or a combination of vibration and noise caused a significant increase in TTSs at 4 and 6 kHz. Moreover, exposure to a combination of vibration and noise caused significantly higher TTSs than exposure to noise at 4 and 6 kHz. Conclusion: The present results demonstrate the combined effects of hand-arm vibration and noise on hearing: simultaneous exposure to hand-arm vibration and noise can enhance the TTS of hearing more than noise exposure, though hand-arm vibration alone may hardly affect TTS. Received: 14 May 1996/Accepted: 20 September 1996     

Efficiency of ear protectors in laboratory and real life tests

Summary The effectiveness of ten different ear-protectors (6 types of earmuffs and 4 types of earplugs) has been tested under laboratory conditions and in the real occupational environment. Three methods were used: (1) physical, utilizing a dummy head; (2) subjective, real-ear, executed on trained human subjects; (3) subjective, measuring TTS₂ resulting from occupational, one-workday exposure. It could be shown that the ear protection efficiency ascertained on the basis of TTS₂ measurements on workers exposed to noise in their occupational environment is, in nearly all cases, smaller than the efficiency expected, taking into account the sound damping of the same protectors, tested under laboratory conditions, using the physical or real-ear method. Measurements of TTS₂ were found to give the best data needed to define the protectors' efficiency, since they include, simultaneously, the impact of various environmental factors, the subjective reactiveness, the nature of the professional task and the acoustical features of the protector used. Therefore this method enables the estimation of the real protection given to workers with a risk of noise-induced hearing loss.     

Simultaneous effects of sinusoidal whole body vibration and broadband noise on TTS2's and R-wave amplitudes in men at two different dry bulb temperatures

The aim of this study was to investigate the temporary hearing threshold shift (TTS2) and R-wave amplitudes in eleven healthy males when they were exposed to paired sinusoidal whole body (Z-axis) vibration (5 Hz--2.12 m/s2) and stable broadband A-weighted white noise at dry bulb temperatures of 20 degrees C and 30 degrees C. The intensity of noise in the exposure combinations was 75, 85 and 95 dB(A). The total number of tests was 66, and they were carried out in an exposure chamber. The subjects were dressed in standard clothing, and carried out simple tasks using a choice reaction time device during the test. According to the results, the means of the TTS2 values were usually higher at the dry bulb temperature of 30 degrees C than at 20 degrees C. Hearing threshold shifts were the greatest at frequencies of 4 and 6 kHz, and the smallest at 8 kHz. The more intense the noise in the paired combination of noise and vibration, the clearer the tendency for an increase in the ambient temperature to accelerate the increase in the hearing threshold. The effect of the ambient temperature on the temporary hearing threshold shifts also appeared to be slightly stronger during successive exposure cycles. Changes in the values for the R-wave amplitudes seemed to be connected with those in the hearing threshold. The decrease in the R-wave amplitude was connected to the increase in the TTS2 values, especially when the subjects were simultaneously exposed to a 95 dB(A) noise and whole body vibration at the dry bulb temperature of 30 degrees C. This implies that an increase in the ambient temperature intensifies cardiovascular disturbances in the body, which accelerate the development of functional disturbance in the inner ear.     

Effects of whole body vibration on biogenic amines in rat brain

The effects of whole body vibration on the concentrations of noradrenaline (NA), dopamine (DA), and serotonin (5-HT) in the whole brain and brain regions of rats were investigated. Compared with control rats, vibration with 20 Hz frequency decreased the brain concentration of NA only when the acceleration (intensity) was increased to 5.0 G (p less than 0.05). The concentration of DA in the whole brain was not affected by acceleration. When acceleration was kept at a constant 0.4 G level and rats were exposed for the same 240 minute period to 5, 20, or 30 Hz vibration, neither NA nor DA concentrations changed in the whole brain. Regional changes in the concentration of biogenic amines in the brain of rats exposed to vibration of 20 Hz and 5.0 G showed few significant differences. Thus NA significantly decreased only in the hypothalamus (p less than 0.01), although in the hippocampus the decrease was nearly significant (p less than 0.10). The concentration of 5-HT significantly increased in the hypothalamus and cerebellum (p less than 0.05). DA tended to increase in the cortex and decrease in the striatum (p less than 0.10). These experiments seem to indicate that NA in the whole brain and especially in the hypothalamus is a better indicator of vibration exposure than 5-HT, and that NA is affected by the intensity but not by the frequency of vibration. NA and 5-HT in the hypothalamus change in the opposite direction. DA concentrations in the brain are basically unaffected by vibration.     

Effects of whole body vibration on biogenic amines in rat brain.

The effects of whole body vibration on the concentrations of noradrenaline (NA), dopamine (DA), and serotonin (5-HT) in the whole brain and brain regions of rats were investigated. Compared with control rats, vibration with 20 Hz frequency decreased the brain concentration of NA only when the acceleration (intensity) was increased to 5.0 G (p less than 0.05). The concentration of DA in the whole brain was not affected by acceleration. When acceleration was kept at a constant 0.4 G level and rats were exposed for the same 240 minute period to 5, 20, or 30 Hz vibration, neither NA nor DA concentrations changed in the whole brain. Regional changes in the concentration of biogenic amines in the brain of rats exposed to vibration of 20 Hz and 5.0 G showed few significant differences. Thus NA significantly decreased only in the hypothalamus (p less than 0.01), although in the hippocampus the decrease was nearly significant (p less than 0.10). The concentration of 5-HT significantly increased in the hypothalamus and cerebellum (p less than 0.05). DA tended to increase in the cortex and decrease in the striatum (p less than 0.10). These experiments seem to indicate that NA in the whole brain and especially in the hypothalamus is a better indicator of vibration exposure than 5-HT, and that NA is affected by the intensity but not by the frequency of vibration. NA and 5-HT in the hypothalamus change in the opposite direction. DA concentrations in the brain are basically unaffected by vibration.     

某汽车制造企业噪声作业工人不同频率听力损失影响因素分析

目的 分析广州市某汽车制造企业噪声作业工人不同频率听力损失状况及各频率听力损失影响因素。方法 以2018年1—12月广州市某汽车制造企业至广州市职业病防治院进行职业健康检查的噪声作业工人为研究对象,对其进行纯音听阈测试、噪声接触水平检测及问卷调查,计算累积噪声暴露量,采用单、多因素分析方法对各频率听力损失发生的影响因素进行分析。结果 2 605名噪声作业工人均为汉族男性,年龄为22（20,24）岁,工龄为3（1,4）年,噪声接触强度为83.50（82.10,86.10）dB（A）,累积噪声暴露量为87.97（85.11,90.81）dB（A）·年。听力损失检出率为34.40%（896/2 605）。左、右耳听力损失检出率,左、右耳语频、高频听力损失检出率的差异均无统计学意义（P>0.05）;左、右耳听力损失检出率均随着频率升高而逐渐增加（趋势χ²值分别为1111.38、1237.14,P<0.01）,且均以6.0 kHz最高。多因素Logistic回归分析显示,吸烟、饮酒与各频率听力损失无显著相关关系（P>0.05）;随着累积噪声暴露量（0.5~6.0 kHz的OR值分别为3.231、4.151、4.809、3.282、2.735、2.069）、年龄（0.5~6.0 kHz的OR值分别为2.167、2.323、2.508、1.776、1.414、1.276）的增加,各频率听力损失风险均逐渐增加（P<0.05）。结论 汽车制造企业噪声作业工人不同频率听力损失以6.0 kHz较为显著,累积噪声暴露量、年龄与各频率听力损失均存在剂量-反应关系。     

Hearing loss of workers in mining--a 6-year longitudinal study

Hearing threshold level (HTL) in miners, was determined after six years interval characterized by the same noise exposure. An attempt was made to establish the prognosis regarding the hearing losses extent and the time interval involved in the occurrence of these modifications in the subjects applying the HTL values. 132 workers (miners and miner apprentices) underwent audiometrical examinations, after 6 years interval in the same testing conditions. To evaluate the vibrations possible effects on the HTL, the results registered in a group of workers exposed solely to noise (n = 33)-identical continuous equivalent level/week-were compared to those found in miners. According to age range and the duration of noise exposure, the yearly mean rate for both the low (500-2000 Hz) and high frequencies (2-8 kHz), were calculated based on the hearing threshold differences. The miners, simultaneously exposed to noise and vibration presented yearly decreased HTL values (up to 2000 Hz), as against the subjects exposed solely to noise. The prognosis indicates that in a miner with a duration of exposure above 21 years and/or a mean age of 38, one may expect a loss of the HTL exceeding 30 dB at 4 kHz.     

An experimental study of the physiological effects of chain saw operation.

This experimental study was designed to determine whether a combination of noise and vibration produced more pronounced changes in temporary shifts of finger skin temperature and temporary threshold shift (TTS) of hearing than those resulting from exposure to either stress alone. Nineteen healthy subjects were exposed to six different combinations of vibration, noise, and handle holding by using a chain saw for a pre-determined time. The mean value of normalised finger skin temperature decreased much more when the subjects operated a chain saw at high speed (exposure 1) than when they operated the chain saw with the noise isolated by double hearing protection (exposure 2). In five of the 14 subjects significantly larger TTS values at 4 kHz were observed in the former condition (exposure 1) compared with the values obtained when they stood beside someone else operating a chain saw (exposure 3). The results of this study suggest that noise may play a part in inducing the constriction of the peripheral vessels seen with local exposure to vibration, and that hand-arm vibration may produce an additive effect on the noise induced TTS.     

An experimental study of the physiological effects of chain saw operation

This experimental study was designed to determine whether a combination of noise and vibration produced more pronounced changes in temporary shifts of finger skin temperature and temporary threshold shift (TTS) of hearing than those resulting from exposure to either stress alone. Nineteen healthy subjects were exposed to six different combinations of vibration, noise, and handle holding by using a chain saw for a pre-determined time. The mean value of normalised finger skin temperature decreased much more when the subjects operated a chain saw at high speed (exposure 1) than when they operated the chain saw with the noise isolated by double hearing protection (exposure 2). In five of the 14 subjects significantly larger TTS values at 4 kHz were observed in the former condition (exposure 1) compared with the values obtained when they stood beside someone else operating a chain saw (exposure 3). The results of this study suggest that noise may play a part in inducing the constriction of the peripheral vessels seen with local exposure to vibration, and that hand-arm vibration may produce an additive effect on the noise induced TTS.     

Isolated and combined effects of prolonged exposures to noise and whole-body vibration on hearing,vision and strain

Summary This study was carried out in order: (1) to examine the effects of isolated and combined prolonged exposures to noise and whole-body vibration on hearing, vision and subjectively experienced strain, and (2) to check the combined effects with repeated exposures. Six male subjects were exposed twice to noise (N) at 92 dBA, whole-body vibration (V) in the Z-axis at 4 Hz and 1.0 ms^–2 rms, and noise and vibration (NV) for 90 min with each condition. Temporary threshold shifts of hearing (TTS) and their integrals (ITTS) were measured at 4, 6, 10, and 12 kHz. Visual acuity was examined by means of a very sensitive test. Cross-modality matching (CMM) of the handgrip force was used to judge the subjectively experienced strain. NV induced a clear tendency of higher TTS and ITTS than N, with several significant differences most pronounced at 10 kHz. With repeated exposures, the effect of NV decreased, while the reactions to N and V remained unchanged. The individual reactions to NV differed. The influence of the duration of exposures on vision depended on the condition; N caused time-dependent changes, whereas V did not. CMM-data increased with the duration of the exposure during V and NV. N was generally judged to be more straining than V; NV caused higher strain than V during the first 30 min of exposure only. Correlations between different effects suggest certain links between them. Additionally, less motivation — daily obtained by a questionnaire — often correlated with higher ITTS during N and NV. The results also illustrate the combined effects on the individual susceptibility, repetition of exposure, the kind of response, and, possibly, the actual psychic state.Abbreviations CMM cross-modality matching - MVC maximum voluntary contraction force - N exposure condition: noise level 92dBA, no whole-body vibration - NV exposure condition: combined exposure to noise with a level of 92 dBA and wholebody vibration with 4 Hz, 1 ms^–2 rms - V exposure condition: whole-body vibration with 4 Hz, 1 ms^–2 rms - TTS temporary threshold shift - ITTS integral of temporary threshold shift - WBV whole-body vibration in the common sense This work was done in the Temporary International Research Team on Combined Effects of Noise and Vibration of the Council of Mutual Economic Assistance of the Socialist Countries. The authors gratefully acknowledge the help and assistance of L.-M. Brumm, Y. Bening, M. Godau, G. Weber, and R. Vizcaino.     

High-frequency hearing loss,occupational noise exposure and hypertension: a cross-sectional study in male workers

Background  

The association between occupational noise exposure and hypertension is inconsistent because of an exposure bias caused by outer-ear measurements of noise levels among workers. This study used hearing loss values (HLVs) measured at 4 kHz and 6 kHz in both ears as a biomarker to investigate the chronic effects of noise exposure on hypertension in 790 aircraft-manufacturing workers.