强噪声暴露后豚鼠听力和血清某些生化指标的变化

５３只白色短毛雄性豚鼠体重３００～４４０ｇ，随机分为６组，每组６～１０只。噪声暴露组和对照组各为３组。暴露噪声频谱是中心频率１ｋＨｚ、带宽１００Ｈｚ的狭带。噪声强度为１２６±１．５ｄＢＳＰＬ。暴露时间３ｈ／ｄ，连续１０天。噪声由Ｂ＆Ｋ１０２７纯音无规发生器产生，经ＪＹ前级增音和４００Ｗ功放后由扬声器组发出。声强由Ｂ＆Ｋ４１４５电容传声器、Ｂ＆Ｋ２６１５阴极输出器及Ｂ＆Ｋ２１０７频率分析仪监测，测量系统经Ｂ＆Ｋ２２３０声级校准器校准。噪声停止后当天（１～３ｈ）、３天（６９～７２ｈ）和９天，分别测定…     

听觉辨别阈的测定

本工作用一种结构简单操作方便的新型调频调幅调相声刺激器，准确地在人（用心理物理方法）和豚鼠（用电生理方法）测定了听觉的频率辨别阈（Δｆ）、强度辨别阈（ΔＩ）和相位辨别阈（Δ）。在听力正常的受试者，测得的Δｆ为１．３±０．６ｐｐｓ（ｐｕｌｓｅｓｐｅｒｓｅｃ．以下同，编者注），ΔＩ为０．４±０．２ｄＢ，Δ为０．９±０．３°。在听力正常的豚鼠，它们相应为２．５±１．１ｐｐｓ，０．５±０．２ｄＢ和１．２±０．５°。文中详细地介绍了所用刺激器的设计及工作原理     

γ射线引起内耳潜在损伤的实验研究

本文报告小剂量γ射线对内耳的潜在影响。研究表明：豚鼠听泡区受到２０Ｇｙ６０Ｃｏγ线照射后，听反应阈无明显偏移，耳蜗行细胞无明显受损。然而，当受照射２０Ｇｙ的豚鼠和未受照射的对照豚鼠同样接受１０５ｄＢＡ的噪声作用３０ｍｉｎ，暴露后８ｈ未受照射的豚鼠仅有６．５ｄＢ的阈移，而受照射豚鼠则有１３．５ｄ的阈移。两者差异非常显著。此外，噪声作用后受照射豚鼠耳蜗毛细胞的损伤较重。结果提示：豚鼠耳蜗在小剂量的γ射     

Fe73.5Cu0.8Nb2V1.2Si11.5B11新型纳米晶合金的研究

报道了Ｆｅ７３５Ｃｕ０８Ｎｂ２Ｖ１２Ｓｉ１１５Ｂ１１新型纳米晶合金的研究结果。透射电镜和穆斯堡尔谱研究表明，合金经８４３Ｋ，０５ｈ真空退火，形成由平均晶粒尺寸为１８ｎｍ左右的αＦｅ（Ｓｉ）相（～７８％）和剩余非晶组成的显微结构。合金的饱和磁感应强度为１４Ｔ，ｆ＝１ＫＨｚ时最大有效磁导率（μｅ）为７１８×１０－３Ｈ／ｍ，Ｐ１２／２ｋ２１ｋＷ／ｍ３，Ｐ１１／１０ｋ２１８ｋＷ／ｍ３，Ｐ０５／２０ｋ１５７ｋＷ／ｍ３，Ｐ０２／１００ｋ３００ｋＷ／ｍ３，矫顽力Ｈｃ≈１１Ａ／ｍ。合金具有明显的磁场处理效果，经纵向和横向磁场退火后，其Ｂ３０、α３０分别为１４４Ｔ，０９０和１３０Ｔ、０１。与Ｆｅ７３５Ｃｕ１Ｎｂ３Ｓｉ１３５Ｂ９相比，由于用Ｖ代替了部分Ｎｂ，提高了熔体流动性，改善了快淬合金带材的机械特性，降低了成本。     

水声换能器微机测量系统

我们研制了一块水声换能器微机测量硬件，插在ＩＢＭ－ＰＣ／ＸＴ微机的系统扩展槽Ｉ／Ｏ通道上。其功能有：（１）可产生２００Ｈｚ～３００ＫＨｚ，脉宽０．５～１０ｍｓｅｃ，重复频率１Ｈｚ～１０Ｈｚ的脉冲调制正弦信号；（２）可产生延时时间为０．１～３０ｍｓｅｃ，选通宽度为０．１～１０ｍｓｅｃ的选通脉冲信号；（３）配合数字存贮示波器ＤＳＳ６５２１可对信号进行采集和运算，根据所编软件，该系统可对水声换能器的方向性和灵敏度进行实时自动测试。     

无Co混合导电型陶瓷透氧膜的制备和性质研究

首次合成了Ｓｒ１０－ｎ／２ＢｉｎＦｅ２０Ｏｍ（ｎ＝２，４，６，８，１０等）系列氧化物透氧膜，它们具有较高的透氧能力，其中，样品ｎ＝１０在１１００Ｋ时的透氧率为０．９０ｍｌ（ＳＴＤ）／（ｃｍ２·ｍｉｎ），比Ｓｒ１－ｘＢｉｘＦｅＯ３高约两倍．Ｓｒ１－ｘＢｉｘＦｅＯ３（ｘ＝０．１，０．３，０．５）系列的透氧率随Ｂｉ含量增加而增大．通过两个系列氧化物的ＸＲＤ和化学组成的对比，发现Ｂｉ离子含量和晶格空位浓度对透氧能力大小起决定性作用．     

LS2p型标准传声器的声中心测量

介绍了ＬＳ２ｐ型标准传声器的声中心测量。测量装置的自由场偏差小于０．１ｄＢ，坐标测距系统准确度优于０．０５％，分辨力为０．０１ｍｍ。声中心测量结果与ＩＥＣ／ＣＤ１０９４－３，２９（ｓｅｃ）２７９标准草案提供的数据进行比较，在２～２０ｋＨｚ频率范围内两者的声中心位置相差±０．１ｍｍ，而在２５ｋＨｚ和３１．５ｋＨｚ两频率分别有５８ｍｍ和１０．０ｍｍ的差别     

Pb（Ni_（1／3）Nb_（2／3））O_3－PbZrO_3－PbTiO_3三

对Ｐｂ（Ｎｉ１／３Ｎｂ２／３Ｏ３－ＰｂＺｒＯ３－ＰｂＴｉＯ３，即ｘＰｂ（Ｎｉ１／３Ｎｂ２／３）Ｏ３－（１－ｘ）Ｐｂ（ＺｒδＴｉ１－δ）Ｏ３（０．２≤ｘ≤０．６，０．２≤δ≤０．５）三元系固溶体的压电性能进行了研究，结果表明材料压电活性较高的配方位于准同型相界（ＭＰＢ）附近，压电常数ｄ３１值可达２６０×１０－１２Ｃ／Ｎ．讨论了结构相变对压电性能的影响．     

工业铯钟速率变化主要因素的探讨

上海天文台（ＳＯ）原子时实验室的４台工业铯钟１９８３～１９９０年连续工作了４或７年，它们的速率的长期变化与钟房的环境参数和性能参数的变化有关。本文根据有关数据，用不同的方法进行了分析，得到了一些明晰的结果。１）钟的速率变化受湿度的季节性变化影响：在相对湿度变化１％时，Ｃｓ２（１２６７）和Ｃｓ４（１４５７４）的速率变化分别为１．８９５ｕｓ／ｄ（２．２×１０－１４）和０．６１８ｎｓ／ｄ（７．１×１０－１５）。ＳＯ的原子钟房的相对湿度的年变化为２０％～８５％，引起这两台钟的速率年变化分别为１．４３×１０－１２和４．６５×１０－１４２）钟的速率变化受钟的离子泵电流参数的线性变化（从钟束管寿命的中期开始）影响：在离子泵电流参数变化１μＡ时，Ｃｓ３（１６１８０）和Ｃｓｌ（１２９９７）的速率变化分别为０．４３９ｎｓ／ａ（５．０８×１０－１５）和０．５５２ｎｓ／ａ（６．３９×１０－１５）。这两台钟的离子系电流参数的年变化分别为１６．４７μＡ／ａ和６．５３μＡ／ａ，引起的频率漂移率分别为１．６７×１０－１３／ａ（０．０３９５ｎｓ／ｄ２）和８．３×１０１４／ａ（０．０１９７ｎｓ／ｄ２）     

城市市区铁路封闭措施研究

以北京站区至北京南站区段铁路环境噪声为例进行测试分析。测量结果表明，鸣笛噪声对环境污染最为突出，比列车在高速（９０ｋｍ／ｈ）运行所产生噪声还高１０ｄＢＡ。而警告性鸣笛每天总次数为４９５次，占总鸣笛的６０％，使噪声值增加９．５￣１６ｄＢＡ。采取城市市区铁路封闭措施，既可降低鸣笛噪声９．５￣１６ｄＢＡ，又可方便和保障居民安全，对我国高速化铁路建设是十分必要的。     

预先暴露低强度噪声对噪声损伤听力保护作用的观察

强噪声暴露可致听力损伤，产生暂时性或永久性听阈偏移。听力损伤程度除和噪声暴露参数有关外，还和听觉系统本身的生理和代谢状态有关［１］。实验证实，外毛细胞在声刺激后有类似耳肌收缩样作用［２］，但这种收缩作用对听力的生物效应还不清楚。低强度无损害性噪声暴露对后来的强声刺激是否有保护作用，国内尚未见有报导。本实验以豚鼠为实验动物，预先暴露低剂量安全噪声，随后暴露能产生听觉损害的强噪声，观察前者对后者的听力损伤有无保护作用。     

Searching for momentum enhancement in hypervelocity impacts

In conjunction with the Los Alamos National Laboratory hypervelocity microparticle impact (HMI) team effort to produce higher impact velocities and to understand the physics of crater formation and momentum transfer, we have implemented a low noise microphone as a momentum detector on both the 6 MV Van de Graaff and 85 KV “test stand” particle accelerators. Calculations are presented showing that the impulse response of a circular membrane. When used as a momentum impulse detector, the microphone theoretically may detect impulses as small as 8.8 × 10⁻¹⁵ N s. Sensitivity of the microphone in this application is limited by the noise threshold of the electronic amplifiers and the ambient microphonic vibration of the system. Calculations lead us to anticipate detection of particles over the full range of the Van de Graaff acceleration capability and up to 7 km/s on the test stand. We present momentum enhancement data in the velocity range between 10 km/s and 20 km/s. Preliminary work is presented on momentum impulse calibration of the microphone using laser-pulse photon momentum as an impulse source.     

Association of work-related accidents with noise exposure in the workplace and noise-induced hearing loss based on the experience of some 240,000 person-years of observation

This retrospective study explores the association between occupational noise exposure at the time of hearing tests, permanent noise-induced hearing loss and work-related accident risk. Log-binomial analysis was used to first ascertain the association between study variables according to activity sector (North American Industry Classification System, NAICS) and accident context while controlling for age. Second part of the paper estimates the overall number of accidents attributable to occupational noise or the associated hearing loss (excess fraction). Study was carried on a sample of 52,982 male workers exposed to a minimum of 80dBA on a daily basis and whose hearing was examined at least once between 1983 and 1996 by public health authorities of Quebec. These participants evidenced bilateral average hearing threshold levels at 3, 4 and 6kHz ranging from normal (/=90dBA) and noise-induced hearing loss.     

夜间单个飞机噪声事件对机场周围居民睡眠的影响分析

文章通过对室地权声暴露级与睡眠唤醒率及扰眠率之间关系的研究,证明了设置夜间单个事件飞机品声限制标准的必要性,并近似拟定１００ｄＢ的室外Ａ计权声暴露级作为夜间单个飞机噪声事件的限制标准。文章具有一定的适用价值和工程意义。     

AANC次级通道建模方法研究

次级通道建模是自适应主动噪声控制（AANC）系统的一个关键问题。应用一种基于时间扩展脉冲（TSP）信号的脉冲响应测量方法。TSP信号具有脉冲能量分布于一段时间的特性,将其作为被测系统的激励,再将其响应信号中的分散能量聚集,即可重构得到系统的脉冲响应函数。该方法被应用于AANC的次级通道建模,仿真和实验分别得到20 dB和14 dB的降噪效果。研究结果表明,该方法实现简单易行,结果准确可靠,非常适用于实际的ANC工程实验。     

Threshold shifts and restitution of the hearing after different music exposures

Human hearing is sometimes exposed to such high levels at modern musical events that the danger of acute damage cannot be ruled out for musicians, disc jockeys and listeners, even if the exposure time is limited. In order to examine at least basically the hypothetically expected different effects of various musical styles, 10 volunteer test subjects were exposed to three types of music with equally loud lower levels. In a change-over test design over several days, quite different exposures (European and Chinese classical music, house music) with a mean level of 94 dB(A) and a limited exposure time of 1 hour were chosen for ethical as well as for pragmatic reasons. Pieces by Bach and Handel, with passages that are dominated by wind instruments, and pieces of the culturally different Chinese music were selected that are fairly similar to European classical music in terms of rhythm and melody, yet completely different with regard to pitch and instrumentation. Since nowadays, many young people prefer music with an emphasis on rhythm to classical music, a medley of monotonous, downright hammering and penetrating house music was used. After the exposures, the maximum hearing threshold shifts (TTS₂) were measured and the entire restitution course was recorded audiometrically. With regression-analytically determined 13.5 dB (house music), 12.1 dB (classical music) and 9.8 dB (Chinese classical music), the TTS₂ values were not substantially different between the three exposures. Based on these results, the aural effects of house music would have been comparable to classical music. However, the restitution of the hearing after house music (with more than 2.5 hours) required a substantially longer time period. After both types of classical music, the resting hearing threshold was once again reached within less than 1 hour. Moreover, the accumulated hearing threshold shifts were substantially (more than three times) lower than the overall physiological costs associated with house music.     

Effects of contrast agent infusion rates on thresholds for tissue damage produced by single exposures of high-intensity ultrasound

Stabilized microbubble ultrasound contrast agents (UCA) have potential to aid tissue ablation during ultrasound surgery by enhancing both cavitational and thermal damage mechanisms. Previously, we showed UCA infused at a rate of 1 microL/kg/min prior to ultrasound exposure could reduce the total energy required to produce tissue damage by up to two orders of magnitude. In this paper, we evaluate thresholds for macroscopic tissue damage with UCA infusion rates (IR) of 0.1, 0.3, 1, 3, and 10 microL/kg/min to determine IR potentially effective for ultrasound therapy. Canine kidneys were surgically externalized and insonified with single exposures of focused ultrasound. Incident exposures were 1.44 MHz tone bursts, either 250 ms in duration with intensity between 500 W/cm2 and 3200 W/cm2, or 100 micros to 1 s in duration with intensity equal to 3200 W/cm2. Probabilities of tissue damage occurrence were determined for each set of exposure conditions (intensity, duration, and IR). A threshold intensity and threshold duration, defined as the quantities for which tissue damage occurred with probability equal to 0.5, were estimated for each IR. Results show that, as IR increased from 0.1 to 10 microL/kg/min, the threshold intensity decreased by up to a factor of 3, and threshold duration decreased by up to a factor of 200. Microbubble introduction at IR up to 10 microL/kg/min thus may be effective in aiding ultrasound therapy.     

急救车车厢内部噪声仿真分析与优化

基于多体系统动力学理论、有限元和边界元方法,使用多种仿真软件建立车身结构有限元模型、整车刚柔耦合系统模型和车厢声学边界元模型,对路面不平度和发动机振动两种激励进行模拟,计算了这两种激励条件下20～150 Hz频率范围内车厢内各场点的A计权声压级。以降低多个场点声压级峰值为目标,综合考虑车厢壁板对各场点声压级峰值的声学贡献度大小和正负性质,对不同壁板组合进行阻尼减振降噪处理,最终确定最佳阻尼降噪方案。结果表明：场点声压级峰值的大小和频率分布与激振力能量的频率分布有关,粘贴阻尼材料在降低噪声的同时,也会改变声压级的频率分布。降噪措施能普遍降低车厢内乘员耳旁的声压级。     

Reduced transposed flicker noise in microwave oscillators using gaas-based feedforward amplifiers

Transposed flicker noise reduction and removal is demonstrated in 7.6 GHz microwave oscillators for offsets greater than 10 kHz. This is achieved by using a GaAs-based feedforward power amplifier as the oscillation-sustaining stage and incorporating a limiter and resonator elsewhere in the loop. 20 dB noise suppression is demonstrated at 12.5 kHz offset when the error correcting amplifier is switched on. Three oscillator pairs have been built. A transmission line feedback oscillator with a Qo of 180 and two sapphire-based, dielectric resonator oscillators (DROs) with a Qo of 44,500. The difference between the two DROs is a change in the limiter threshold power level of 10 dB. The phase noise rolls-off at (1/f)(2) for offsets greater than 10 kHz for the transmission line oscillator and is set by the thermal noise to within 0-1 dB of the theoretical minimum. The noise performance of the DROs is within 6-12 dB of the theory. Possible reasons for this discrepancy are presented.     

Sensitivity and Dynamic Range Considerations for Homodyne Detection Systems

The effects of modulation frequency, RF reference power, and external bias upon the sensitivity and dynamic range of microwave homodyne detection systems was measured for point contact diodes and low l/f noise Schottky and backward diodes. The measurements were made at 4.89 GHz using a signal to noise ratio of 3 dB and a detection system bandwidth of 10 Hz. Maximum sensitivities of -135, -150, and -145 dBm, and dynamic ranges of 92, 110, and 124 dB were measured for the point contact, Schottky, and backward diodes at modulation frequencies of 30, 30, and 3 kHz, respectively. It was found that the level of RF reference signal needed to obtain the maximum sensitivity was equal to or somewhat above the point where the diode changes from square law to linear detection. The results are significant in that previously reported homodyne sensitivities (not necessarily maximum) were on the order of -90 to -130 dBm for point contact diodes and no data are available for Schottky and backward diodes. Significantly improved stability, sensitivity, and dynamic range can be achieved using these low 1/f noise devices, the correct external bias, and the optimum RF reference power.