歼（强）击机座舱噪声限值制定的研究

本研究的目的是根据现场调查和实验研究的结果，参考国内外有关标准，并结合我国航空工业实际，综合分析制定了歼(强)击机座舱噪声限值标准。要求在这个限值以内不造成飞行员的听力损害、工作效率的降低，确保正确无误地进行无线电通讯联系。根据以上考虑，座舱内噪声通过头盔耳机传入飞行员耳内的声级应不超过90dB(A)，加上头盔的声衰减值20dB，座舱噪声跟值定为108dB（A)是可行的。     

在三种中等强度噪声下暴露60天豚鼠的听阈偏移及其恢复特征

豚鼠在三种中等强度哚声的暴露过程中,当实验期为15～30天时,95dBA 组的听觉偏移迅速增加并达到最大值,而后稳定在20～23dB 的范围.85和90dBA 组的听阈偏移差异很小,实验期为60天时,两组的偏移基本相等,约9dB。噪声暴露结束后21天内,95dBA 组保持18—20dB 的偏移水平,而后逐渐减少,但75天后不再继续恢复,大约维持在12dB 左右的偏移水平。90dBA 组,听力的恢复较为缓慢,30天后仍有7dB 的偏移。而85dBA 组,暴露后21天内,恢复较快。     

高原藏、汉族创伤失血性休克患者对液体耐受能力的差异及对策

目的探讨高原地区(海拔3 658m)藏、汉族创伤失血性休克患者休克早期对复苏液体耐受能力的差异及对策。方法通过对332例高原世居藏族(A组)、216例高原移居汉族(移居高原3个月以上,B组)和18例急进高原汉族(进入高原1周以内,C组)中度创伤失血性休克的有关资料进行回顾性比较、分析研究,找出他们的早期液体复苏的特点及规律。结果C组患者早期可耐受晶体液为失血量的1~1.5倍,维持血压所需的胶体液用量约为失血量的1~1.5倍(晶胶比约为1:1),总量不超过总失血量的2.5倍,输液速度以0.5~1.0m l/(kgB.W..m in)为宜;B组患者可耐受的晶体液为失血量的1.5~2倍,维持血压的胶体液用量约为失血量的0.75~1倍(晶胶比约为2:1),总量不超过3倍,输液速度先快[1~1.5m l/(kgB.W..m in)]后慢;A组患者晶体液可达3~4倍以上,早期可不输或输0.5倍失血量的胶体液(晶胶比约为4:1),耐受快速输液1.5~2.0m l/(kgB.W..m in)。结论C组患者液体耐受能力显著低于B组患者,B组又显著低于A组。提高晶胶液体比例、放慢输液速度、延长持续复苏时间、保护肺脑组织细胞、应用高渗液体等措施可增加失血性休克的早期液体输入量。     

容积旋转调强计划计算分辨率对COMPASS验证通过率的影响

目的 研究容积旋转调强放疗（VMAT）计划设计采用不同计算分辨率对COMPASS验证通过率的影响。方法 选取10例宫颈癌术后患者,在治疗计划系统上采用4种计算分辨率0.2 cm×0.2 cm×0.2 cm、0.3 cm×0.3 cm×0.3 cm、0.4 cm×0.4 cm×0.4 cm、0.5 cm×0.5 cm×0.5 cm设计VMAT治疗计划。计划传至加速器上执行,由COMPASS实际测量重建并与TPS优化的剂量分布进行比较得到每个计划的偏差值,统计分析4种计划的偏差值是否有统计学意义。结果 肿瘤靶区的D_mean和D₉₅,COMPASS测量重建结果表明D_mean偏差值的平均值<0.5%,D₉₅<1.3%,标准差均<1.0%。对于4种计划危及器官（OAR）,其中左右股骨头的D_mean偏差值最大可达-6.7%、-7.0%、-8.0%、-5.8%,直肠V₃₅偏差值最大可达-4.9%、-6.3%、-6.1%、-5.7%,是OAR中相应参数偏差值最大的两个器官。肿瘤靶区的γ通过率都在95%以上,标准差不超过2.5%;OAR除了股骨头γ通过率略低,在95%以上,标准差1.9%~6.1%不等,其余都达到98%以上,标准差<2.5%,差异均无统计学意义（P>0.05）。平均γ值的分析结果与γ通过率相一致,除了股骨头的平均γ值>0.4外,PTV和其余OAR的平均γ值都<0.4,差异均无统计学意义（P>0.05）。结论 采用0.2~0.5 cm计算分辨率优化宫颈癌术后VMAT计划,不影响COMPASS验证通过率。     

诱发电位的特征分析用作麻醉深度的监测(Ⅰ)——芬太尼对猫中潜伏期听觉诱发电位的影响

准确地监测病人术中麻醉深度具有重要的临床意义,特别是现代复合麻醉技术的应用给医生判断麻醉深度带来了更大的困难。迄今为止,仍然没有一个客观、简便且准确的监测麻醉深度的方法。针对这一问题,本文通过分组动物实验,研究了芬太尼对猫中潜伏期听觉诱发电位(MLAEP)的影响,以探讨用诱发电位作为麻醉监测手段的可能性,并为临床提供有效、客观监测指标。将21只猫随机等分成三组:A组高浓度芬太尼组、B组空白对照组和C组低浓度芬太尼组。用苯巴比妥钠镇静之后,给肌松药并插管人工控制呼吸。芬太尼或等量生理盐水分三次由静脉注射,每次间隔20min,给总量的1/3。在给药前及每次给药后5min和15min时分别记录左右耳MLAEP,模拟信号频率范围10～250Hz,描记后经数字化送入计算机。记录电极置于头顶,左右耳后为参考。由波宽100μs的方波送入耳机产生短声刺激,刺激频率9.7次/s,刺激强度90dB听力级。MLAEP扫描时间50ms,迭加次数512次。数字信号采样率1.28kHz。A组动物在每次记录MLAEP的同时采动脉血样以测室血中芬太尼含量。随机选取9只动物做血气分析。实验过程中监测动物动脉血压及体温并维持恒定。首先,分析了芬太尼对猫MLAEP时域特性,即Na、Pa潜伏期和Pa幅值的影响。之后,用参数模型(11阶AR模型)方法做MIAEP信号的功率谱估计,研究了芬太尼对猫MLAEP信号谱峰位置的影响。进而,利用所建立的参数模型,提取5阶AR模型的系数、模型极点分布等特征量,寻找能准确反映麻醉深度的客观指标。经过组内分析和组间比较,得出:1.芬太尼对猫MLAEP的Na、Pa潜伏期及Pa幅值没有显著影响。2.芬太尼对猫MLAEP信号的功率谱谱峰位置没有显著影响。3.猫MLAEP信号的AR模型系数|A_1|和模型极点分布复平面上“小幅角”θ的大小随猫血中芬太尼浓度的增加明显减小。上述结果表明,本文所提出的MLAEP信号的AR模型特征量可以比其时域特性更敏感地反映芬太尼的作用,因此当芬太尼的用量与麻醉深度的关系建立以后,可以作为监测麻醉深度的客观指标。我们建议临床上利用MLAEP监测麻醉深度时,应同时考虑其时域和频域的多种参量,以确保判断结果的可靠性。     

复合护耳器通话及防护效果的研究

为了研究单一护耳器和复合护耳器通话及防护效果，对１４名男性被试者，分别进行了声衰减性能和通话效果实验。结果表明，单一护耳器经复合使用后，其声衰减值比单一的耳塞、耳罩分别高出１３和６ｄＢ，并且还可克服单一护耳器在某些频率上出现的谐振点所造成声衰减性能降低的缺陷。单一护耳器经复合使用后，克服了听觉器官过载造成的畸变，基本上保持了原有的通话质量，复合护耳器是航空航天噪声环境中的有效耳防护设备。     

Balancing speech intelligibility versus sound exposure in selection of personal hearing protection equipment for Chinook aircrews.

BACKGROUND: Aircrews are often exposed to high ambient sound levels, especially in military aviation. Since long-term exposure to such noise may cause hearing damage, selection of adequate hearing protective devices is crucial. Such devices also affect speech intelligibility. When speech intelligibility and hearing protection lead to conflicting requirements, a compromise must be reached. The selection of personal equipment for RNLAF Chinook aircrews is taken as an example of this process. METHODS: Sound attenuation offered by aircrew helmets and ear plugs was measured using a standardized method. Sound attenuation results were used to calculate sound exposure. Objective predictions of speech intelligibility were calculated using the Speech Transmission Index (STI) method. Subjective preference was investigated through a survey among 28 experienced aircrew members. RESULTS: The use of ear plugs in addition to a (RNLAF standard) helmet may lead to a significant reduction of sound exposure. Using ear plugs that offer high sound attenuation, instead of using a less attenuating type, gives a little additional reduction of sound exposure, at the expense of a large reduction in speech intelligibility. Hence, it is better to use 'light' ear plugs. Better performance still is offered by Communications Earplugs, ear plugs featuring integrated miniature earphones. Results from the user preference survey correspond well with objective measurement results. CONCLUSIONS: In the case of the RNLAF Chinook, the best solution is using Communications EarPlugs in combination with a standard helmet. The Chinook case clearly illustrates that hearing protection and speech intelligibility should be treated as connected issues.     

Double hearing protection and speech intelligibility-room for improvement

INTRODUCTION: Double hearing protection is used in many air forces around the world for protection in noisy aircraft environments, particularly in helicopters. The usual combination is foam ear plugs under headset or helmet muffs. Much of the research that spurred the introduction of foam earplugs indicated little change in speech intelligibility in persons with normal hearing. However, aircrew often complain about having to maximize intercom volume for speech understanding, causing a situation with no reserve volume and bad sound quality. In recent years, further developments have included so-called hi-fi plugs and custom made ear plugs which are claimed to improve speech communication. The aim of the present project was to investigate different types of ear plugs and their effect on speech intelligibility in helicopter noise. METHODS: Each of nine normal-hearing pilot subjects were placed in an environment of recorded helicopter noise from a BO-105 helicopter. Speech audiometry was performed under four different conditions: headset only, and three different ear plugs worn under the headset. Fitting of the ear plugs was performed by an ear, nose and throat specialist to ensure similar conditions. The sequence of test conditions was randomized and double-blind. In addition, a subjective rating scale was used. RESULTS: Wearing foam ear plugs under the headset decreased speech intelligibility dramatically. The "hi-fi" plug was somewhat better than foam plugs, and the custom made ear plug provided a speech intelligibility close to the headset-only situation. Subjective rating scores coincided with these findings. DISCUSSION: In helicopter noise, custom made ear plugs may provide a much improved speech intelligibility over conventional plugs when worn under a headset, while maintaining improved noise protection over the headset-alone situation. Custom made ear plugs might therefore be a good alternative to other forms of enhanced noise protection in helicopters.     

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.     

Speech intelligibility in noise using throat and acoustic microphones

INTRODUCTION: Helicopter cockpits are very noisy and this noise must be reduced for effective communication. The standard U.S. Army aviation helmet is equipped with a noise-canceling acoustic microphone, but some ambient noise still is transmitted. Throat microphones are not sensitive to air molecule vibrations and thus, transmittal of ambient noise is reduced. It is possible that throat microphones could enhance speech communication in helicopters, but speech intelligibility with the devices must first be assessed. In the current study, speech intelligibility of signals generated by an acoustic microphone, a throat microphone, and by the combined output of the two microphones was assessed using the Modified Rhyme Test (MRT). METHODS: Stimulus words were recorded in a reverberant chamber with ambient broadband noise intensity at 90 and 106 dBA. Listeners completed the MRT task in the same settings, thus simulating the typical environment of a rotary-wing aircraft. RESULTS: Results show that speech intelligibility is significantly worse for the throat microphone (average percent correct = 55.97) than for the acoustic microphone (average percent correct = 69.70), particularly for the higher noise level. In addition, no benefit is gained by simultaneously using both microphones. A follow-up experiment evaluated different consonants using the Diagnostic Rhyme Test and replicated the MRT results. DISCUSSION: The current results show that intelligibility using throat microphones is poorer than with the use of boom microphones in noisy and in quiet environments. Therefore, throat microphones are not recommended for use in any situation where fast and accurate speech intelligibility is essential.     

环境噪声对声信号频率辨别阈的影响

目的：通过环境噪声对人体接收不同声信号频率辨别阈影响的试验,寻找某种具有抗噪声干扰的特殊信号,为研究抗噪声言语通讯装置提供理论依据。方法：选取3种调制波,即纯音调频信号,调幅调频信号和方波,作为测试声信号,为研究抗噪声言语通讯装置提供理论依据。方法：选取3种调制波,即纯音调频信号,调幅调频信号和方波,作为测试声信号,采用阈上测试法,以阈上40dB信号辨别阈值为对照,分别测定S（信号）／N（噪声）比为0,－5,－10的频率辨别阈,结果：以上3种信号的频率辨别阈为方波最佳,调幅调频波次之,纯音信号最差,结论：本试验为抗噪声言语通讯开拓了新途径,言 若采用经调制后的方波或调幅波传递,将会获得满意的可懂度。     

噪声、振动复合因素对汉语语音清晰度影响的研究

目的 探讨噪声、振动复事因素下生成语音在听觉效果上的变化及变化规律。方法 在安静及信噪比分别为０ｄＢ和－６ｄＢ三种状态下进行清晰度测试,以研究噪声、振动复合因素组、单独噪声组、单独振动组及对照组４个组的语音材料清晰度变化规律。结果 和对照组相比,复合因素作用下语音清晰度有明显降低,检验结果非常显著;和单因素相比,多数情况下有显著性变化。研究还发现,清晰度的降低随听音环境的信噪比的降低而变得严重,当     

Inter- and intra-individual variation in applied force when listening at a surface, and resulting variation in earprints

We aimed to explore the level of inter- and intra-individual variation in applied force when listening at a surface, and assess the resulting variation in earprints. We further intended to identify possible sources of this variation. Forty subjects each listened twenty-four times at a surface while applied force was recorded. In between efforts the level and frequency of the target sound, and the level of ambient noise were varied. Each listening effort was characterized by two values: the mean of a series of force recordings ('functional force') and the highest force reading of the effort ('peak value'). A mixed model analysis of variance revealed that repetition during multiple efforts of listening and the level of the target sound significantly affected both values for applied force. The frequency of the target sound affected the peak value, but we assume this was due to confounding effects. The level of ambient noise did not affect applied force. To explore the correlation between values for applied force of various efforts by single ear, the intra-class correlation coefficient was calculated. For functional force it was 0.80; for the peak value it was 0.79. To study intra-individual variation in earprints, five prints from each ear were lifted and studied. Variation in prints is discussed.     

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.     

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.