掩蔽声对豚鼠听阈和频率辨别阈的影响

目的：探讨噪声对听觉辨别功能的影响及其作用规律，为特殊作业环境噪声控制提供参考依据。方法：用纯音和重复短声调频诱发的慢反应阈值作为指标，利用平均叠加技术测定清醒豚鼠在安静状态无外加噪声和在７５、８０、８５、９０与９５ｄＢＡ５种强度噪声掩蔽下的听阈和频率辨别阈变化。结果：听阈随掩蔽声强度的增加而递增。暴露强度为７５～８５ｄＢＡ，频率辨别阈（Δｆｒ）变化不明显，当强度增加到９０～９５ｄＢＡ时，Δｆｒ显著增加，与安静状态无外加噪声比较差异十分显著。结论：当环境噪声≤８５ｄＢＡ时，只要将接收信号声调节到阈上１０～１５ｄＢ，就能得到满意的辨别效果；当环境噪声＞９０ｄＢＡ时，即使将接受信号声提高到较高水平，听觉辨别功能仍会出现明显影响，这时应考虑采取隔声减噪措施。     

航空铆接噪声作业工人听力损伤分析

目的；分析接触航空铆接噪声作业工人听力损伤，方法：对４个车间２２个作业点进行监测，对２４７名接触者进行体检及８个频率段听阈值测定，结果：噪声强度最高为１２２ｄＢ（Ａ）；１２３ｄＢ（Ｂ）；１１７ｄＢ（Ｃ），最低为８６ｄＢ（Ａ）；８９ｄＢ（Ｂ）；８６ｄＢ（Ｃ），平均为１０６ｄＢ（Ａ）；１０５ｄＢ（Ｂ）；１０４ｄＢ（Ｃ）。等儿连续Ａ声级强度最高１０７ｄＢ，最低１０４ｄＢ。１７９人有不同程度的听力损伤（男     

速可眠,三唑仑,褪黑素催眠效果的电生理特征及其对脑功哪

目的 比较速 可眠（ＳＥＣ）、三唑仑（ＴＺＬ）、褪黑素（ＭＬＴ）催眠的电生理特征，探讨其对脑功能防护的可能性。方法 在模拟歼－６飞机噪声干扰环境中（１５０ Ｈｚ、９５ｄＢ），观察上述三种药物对８名健康男性青年志愿者（１８￣２０岁）多导睡眠图（ＰＳＧ）指标的影响，即对醒觉时间（ａｗａｋｅ ｔｉｍｅ，ＡＴ）、睡眠潜时（ｓｌｅｅｐ ｌａｔｅｎｃｙ，ＳＬ）、实际睡眠时间（Ａｃｔｕａｌ ｓｌｅｅｐ ｔｉｍｅ     

噪声对人思维能力的影响

目的观察中等强度噪声对人的思维作业绩效的影响。方法在８５、９０ｄＢ（Ａ）暴露２ｈ期间,２４名健康青年男性受试者进行了连续计算、连续减法及识符检数作业任务测试。结果 在８５ｄＢ（Ａ）噪声条件下暴露１ｈ,与对照比较,被试者连续计算的正确率,在一定时间内计算总数、正确数元显著改变;但连续减法一定时间内正确数、计算总数均显著降低。在９０ｄＢ（Ａ）噪声暴露３０ｍｉｎ及２ｈ识符检数的平均反应时,反应时绩效均较     

稳态与脉冲噪声协同作用对豚鼠内耳损伤的研究

目的：观察稳态噪声、脉冲噪声与两者协同作用下对豚鼠内耳的损伤。方法：正常豚鼠９６只，分为３组，（１）稳态组：接受１１０ｄＢＡ稳态噪声４小时，连续３天；（２）脉冲组：接受脉冲噪声峰压值为１６５ｄＢＡ的爆震１０发；（３）稳态＋脉冲组：暴露于稳态噪声３天后休息２小时再接受脉冲噪声１０发。测豚鼠皮层诱发电位及观察耳蜗火棉胶包埋标本、铺片标本。结果：３组分别噪声刺激后对豚鼠听阈及内耳形态学均有影响，以稳态组最轻，稳态＋脉冲组最重。结论：在噪声环境中工作的艇员应加强对内耳的防护，以减少爆震性耳聋的发生。     

噪声对人心理旋转能力的影响

为探讨低频中等强度噪声对人的心理旋转作业绩效的影响，２４名健康青年男性在８５、９５ｄＢ（Ａ）噪声下，进行了心理旋转和判别方向作业任务测试。结果显示：在８５ｄＢ（Ａ）噪声条件下暴露１２０ｍｉｎ期间，与对照组比较，心理旋转的平均反应时显著延长（Ｐ＜０．０５），反应时绩效和综合绩效显著下降（Ｐ＜０．０１）；暴露１２０ｍｉｎ时的反应时绩效和综合绩效均显著高于暴露３０ｍｉｎ时的作业绩效（Ｐ＜０．０５）。在９５ｄＢ（Ａ）噪声条件下暴露１２０ｍｉｎ期间，与对照组比较，判别方向的平均反应时显著延长（Ｐ＜０．０１），反应时绩效和综合绩效显著下降（Ｐ＜０．０１）；暴露１２０ｍｉｎ时的反应时绩效显著高于暴露３０ｍｉｎ时的作业绩效（Ｐ＜０．０５）。本实验８５、９５ｄＢ（Ａ）两种强度噪声条件下暴露２ｈ，对心理旋转作业任务的绩效有一定的影响，表明在卫生学标准容许范围的中等强度噪声对较为复杂或脑力负荷较大的作业任务的工效会有一定的影响。     

短期中度噪声条件下情感状态的变化(英文)

目的研究中等强度噪声条件下２ｈ暴露期间情绪状态的改变及其与受试者噪声敏感度和艾森克人格个性的相关关系。方法１４名男性受试者随机暴露于５０ｄＢ（Ａ）（对照），７５ｄＢ（Ａ）和８５ｄＢ（Ａ）２ｈ期间，于０．５ｈ，１ｈ和２ｈ进行ＰＯＭＳ问卷测试。结果“紧张”等不良情绪评分随噪声强度的增加而增加，精力充沛评分则下降。在２ｈ暴露期间，不良情绪评分逐渐增加，精力充沛评分则在０．５ｈ增加，１ｈ恢复至对照水平，以后又下降。在噪声暴露早期，噪声敏感度高的受试者其精力充沛评分较噪声敏感度低的受试者高；ＥＰＱ中Ｅ分与疲劳等不良情绪评分的增加值有正相关关系。结论噪声对受试者的情绪有一定的影响，其与受试者的噪声敏感度和艾森克人格个性有一定的关系。     

坦克噪声与榴弹脉冲声复合因素对耳损伤的动物实验

为探讨复合因素对耳损伤的机制，将豚鼠分为４组：单独振动噪声组（１１６－１１８ｄＢ（Ａ）），单独脉冲声组（榴弹射击３发，声强１６９ｄＢ（ＳＰＬ），Ｂ有效持续时间５０ｍｓ，振动噪声加脉冲声组和对照组，用脑干电反应的检测听力，用组织化学耳蜗病变结果表明，单独因素未致动物耳损伤，而复合因素组动物听力下降且有耳蜗酶活性下降。     

噪声水平与性格特点对人操作者不同难度跟踪作业工效的影响

通过计算机模拟，研究了８名被试在５７、８０、９０、９５、１００ｄＢ（Ａ）五种噪声水平下的跟踪作业工效，作业设置三种难度，其被控对象分别为：一阶环节０．５／Ｓ和０．５／Ｓ（０．２５Ｓ＋１）、二阶环节０．５／Ｓ＾２，实验前对被试进行１６ＰＦ心理素质测定。结果表明：８０ｄＢ（Ａ）噪声环境下三种难度的跟踪工效均优于基佗几种噪声水平下的结果，但差异不具有显著意义，操作者性格特点对高难度踊跃作业工效有显著的曩     

γ射线与噪声对豚鼠听觉损伤的复合效应

研究了γ射线（２０Ｇｙ）与噪声（１０５ｄＢＡ，３０ｍｉｎ）一次联合作用及６次重复联合作用（每次γ射线０．６７Ｇｙ，噪声１００ｄＢＡ，３０ｍｉｎ），对豚鼠听觉损伤的复合效应。结果表明，先γ射线２０Ｇｙ照射后噪声暴露对听觉损伤的复合效应是协同的。６次重复联合作用时，先噪声暴露后照射组的听阈偏移小于先照射后噪声暴露组；前者的复合效应为拮抗，后者为相加。本文对γ射线与噪声对听觉损伤联合作用的机理作了初步探讨。     

Noise attenuation of hearing protectors against heavy weapon noise

This study evaluated the noise attenuation of earplugs and earmuffs or their combined use against heavy weapon noise in field conditions for military personnel. The noise attenuation was measured with a miniature microphone inserted into the ear canal. The subjects (13) were tested against pink noise and against the noise of explosions and bazooka, mortar, cannon, and howitzer. The attenuation (insertion loss) was 16 to 23 dB for earplugs, 10 to 20 dB for earmuffs, and 24 to 34 dB for the combined use of plugs and muffs. The transfer function of an open ear was 5 to 7 dB when measured as the C-weighted peak level. The combined use of earplugs and earmuffs gave smaller attenuation values than expected. If the limit for the C-weighted peak level is 140 dB for unprotected ears, then protection against low-frequency noise is provided for up to 156 dB by earplugs, up to 150 dB by earmuffs, and up to 165 dB by the combined use of plugs and muffs.     

Arousal from sleep: the physiological and subjective effects of a 15 dB(A) reduction in aircraft flyover noise.

The present research was concerned with whether or not a 15 dB(A) reduction in overall noise level would lessen the sleep disturbing properties of jet aircraft flyover noise and, if less disturbing, whether this would be subjectively appreciated by the sleeping individual. The results indicate that a reduction of 15 dB(A) does result in less sleep disruption but only during sleep characterized by fast-wave electroencephalographic activity. During sleep characterized by slow-wave electroencephalographic activity, such a reduction in the sleep-disturbing properties of jet aircraft noise has little effect. Moreover, even when effective during fast-wave sleep, the decreased arousal produced by the lower noise levels is not subjectively appreciated by the individual in terms of his estimate of the quality of his night's sleep. Thus, reducing the overall noise level of jet aircraft flyovers by some 15 dB(A), is, at best, minimally beneficial to sleep.     

Performance and quality of sleep wearing NBC protective clothing

Two separate studies were carried out to investigate the effect of wearing nuclear-biological-chemical aircrew equipment assembly (NBC AEA) protective clothing on performance and on overnight sleep. Performance at a series of tasks was measured, in six male subjects, during the day (0800-2000 hours) and at night (2000-0800 hours). Wearing the NBC assembly did not lead to significant decrements in performance compared with the normal aircrew equipment assembly (AEA). The sleep of six male volunteers was recorded electroencephalographically on two consecutive nights when NBC protective clothing was worn. Sleep was both shortened and disturbed, compared with overnight control sleep. There were some improvements on the second night, suggesting that individuals may adapt to wearing the NBC assembly.     

Auditory localization in the horizontal plane with single and double hearing protection

INTRODUCTION: Although single hearing protection devices such as earplugs or earmuffs are known to degrade sound localization, little is known about localization accuracy in double-hearing-protection conditions where both earplugs and earmuffs are worn at the same time. METHODS: Listeners wearing earplugs, earmuffs, or a combination of earplugs and earmuffs were asked to localize short (250 ms) or long (continuous) pink noise signals originating from one of 24 loudspeaker locations in the horizontal plane. RESULTS: When single hearing protection was worn, localization was reasonably accurate in the left-right dimension even when the stimuli were short in duration. When double hearing protection was worn, however, left-right localization accuracy was poor even when the stimuli were on continuously. A second experiment showed that localization accuracy with double hearing protection varied substantially across different listeners, but that it varied only slightly across refittings of the same earplugs and earmuffs on the same listener. A third experiment showed that double hearing protection impaired localization in the left-right dimension much more for narrow-band sounds at frequencies above 500 Hz than it did for narrowband sounds at frequencies at or below 250 Hz. DISCUSSION: The severe disruptions in performance that occurred when earmuffs and earplugs were worn simultaneously suggest the influence of a mechanism such as bone conduction that does not normally interfere with localization when only a single hearing protection device is used.     

Verbal communication in MR environments: effect of MR system acoustic noise on speech understanding

PURPOSE: To assess the masking effect of magnetic resonance (MR)-related acoustic noise and the effect of passive hearing protection on speech understanding. MATERIALS AND METHODS: Acoustic recordings were made at 1.5 T at patient and operator (interventionalist in the MR suite) locations for relevant pulse sequences. In an audiologic laboratory, speech-to-noise ratios (STNRs) were determined, defined as the difference between the absolute sound pressure levels of MR noise and speech. The recorded noise of the MR sequences was played simultaneously with the recorded sentences at various intensities, and 15 healthy volunteers (seven women, eight men; median age, 27 years) repeated these sentences as accurately as possible. The STNR that corresponded with a 50% correct repetition was used as the measure for speech intelligibility. In addition, the effect of passive hearing protection on speech intelligibility was tested by using an earplug model. RESULTS: Overall, speech understanding was reduced more at operator than at patient location. Most problematic were fast gradient-recalled-echo train and spiral k-space sequences. As the absolute sound pressure level of these sequences was approximately 100 dB at patient location, the vocal effort needed to attain 50% intelligibility was shouting (>77 dB). At operator location, less effort was required because of the lower sound pressure levels of the MR noise. Fast spoiled gradient-recalled-echo and echo-planar imaging sequences showed relatively favorable results with raised voice at operator location and loud speaking at patient location. The use of hearing protection slightly improved STNR. CONCLUSION: At 1.5 T, the level of MR noise requires that large vocal effort is used, at the operator and especially at the patient location. Depending on the specific MR sequence used, loud speaking or shouting is needed to achieve adequate bidirectional communication with the patient. The wearing of earplugs improves speech intelligibility.     

Effectiveness of foam earplug hearing protection for artillerymen firing L118/119 105 mm howitzers

A field study was carried out to study the effect of firing the British L118/9 195 mm howitzer (Hamel gun) on the hearing of crewmen wearing EAR earplugs. Two guns and gun crews were placed 7 m apart, each gun firing 40 rounds during each of 2 successive days. Bekesy type audiometry was carried out before and after firing and was also used to measure the attenuation or goodness of fit of the earplugs. No significant hearing loss was measured in any of the crewmen. It was concluded that, if correctly fitted, EAR earplugs provide adequate hearing protection under these exposure conditions.     

Periodic breathing and O2 saturation in relation to sleep stages at high altitude

This study was designed to compare sleep organization at high altitude (HA) and sea level (SL) and to estimate the extent periodic breathing (PB) negatively influences arterial O2 saturation (SaO2). Six lowlanders were studied at SL and after 3 weeks spent at 3,800 m (La Paz, Bolivia). Three EEG leads, EOG, submental EMG, chest and abdominal motion, temperature of ventilated gas, and SaO2 were polygraphically recorded. Comparison of HA and SL data disclosed that: 1) Sleep organization was identical, with the same percentage of REM and stage 4. 2) PB (cycle length: 20 s; central apnea: 9 s) occurred in three subjects during all stages of sleep except REM (43-60% of total sleep). A periodic lowering in heart rate occurred during ventilatory oscillation. 3) During PB, SaO2 oscillated very regularly from 78-90%, which resulted in a mean SaO2 value calculated during oscillations similar to that of the non-periodic breathers. We conclude that lung O2 uptake during PB is preserved.     

Determination of gradient magnetic field-induced acoustic noise associated with the use of echo planar and three-dimensional,fast spin echo techniques

The purpose of this study was to assess gradient magnetic-field-induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three-dimensional fast spin echo (3D-FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field-strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D-FSE pulse sequences. Parameters were selected to produce “worst case” acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A-weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D-FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.     

Sound attenuation from earmuffs and earplugs in combination: maximum benefits vs. missed information

INTRODUCTION: Noise levels from military aircraft range from 100-130 dBA. Peak pressure levels from large caliber weapons may reach 180 dB SPL. To protect against hearing loss, individuals are encouraged to wear double hearing protection. This study determined ways to maximize benefit. METHOD: Hearing thresholds from 0.25-8 kHz and consonant discrimination were assessed in normal-hearing subjects with ears unoccluded and fitted with highly rated earmuffs and earplugs, singly or in combination. The earplugs were available in two sizes. Selection was based on best fit. Attenuation values were derived from the threshold measurements. RESULTS: With the muff, plug, and muff and plug in combination, thresholds ranged from 35-48 dB SPL, 40-55 dB SPL, and 44-66 dB SPL, respectively, across the frequencies tested. The combination (without regard to size of plug) resulted in attenuation values of 38-54 dB. With the smaller of the two plugs, low-frequency values as high as 53-61 dB were realized. Consonant discrimination decreased by 6-8% with the devices worn singly and by 22% with the devices in combination, relative to unoccluded listening. DISCUSSION: Sufficient low-frequency attenuation may be achieved with muffs and plugs in combination to prevent hearing loss from operational noise. Attenuation may be maximized by choosing a smaller earplug to achieve a better fit. Possible downsides are reduced detection of warning sounds and speech intelligibility. To be heard warning sounds should surpass protected thresholds by at least 5 dB. Choosing devices which provide somewhat less attenuation may be necessary to preserve communication capability.