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声频放大器由于元器件的质量和外部影响,会出现噪声(noise),降低信噪比。声频放大器的噪声可分:①规则噪声,如交流声;②连续的不规则噪声,如随机的热噪声、散粒噪声;③间歇噪声或瞬时噪声,这类断续或间歇的“喀呖”噪声大多是外来噪声,由邻近或共用同一电源线的工业设备及家用电器在间歇工作时产生,也可能由于连线不牢靠或虚焊引起。电子管放大器内部产生的噪声,有热噪声、散粒噪声、闪烁噪声、颤噪效应噪声、接触噪声及交流声。热噪声(thermalnoise)来源于电阻中电子的热骚动,它决定了电路中的噪声下限。电路中的元件只要它们消耗能量,就会… 相似文献
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民用飞机噪声航迹的计算是飞机噪声合格审定的一个重要环节,计算飞机的起飞噪声航迹及进场噪声航迹,作为声学专业进行起飞横测基准噪声、飞越基准噪声以及进场基准噪声计算的输入数据,以及噪声试飞的基准航迹。本文通过对适航条例的研究分析,建立了符合适航规章规定的民用客机噪声航迹的计算程序,可用于民用飞机噪声航迹的计算,供适航合格取证使用。 相似文献
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作为空调外机的主要噪声振动源之一,压缩机对于外机噪声的影响至关重要。但由于受到隔声处理、压缩机振动诱发结构噪声以及其它重要噪声源等诸多因素的影响,导致压缩机噪声振动与空调外机噪声之间的关系复杂化。通过理论与实验分析,对某型直流变频空调外机噪声与压缩机单体噪声振动进行了研究。结果表明:压缩机噪声与空调外机噪声之间不是简单的线性关系,压缩机噪声的大幅度降低并不意味着空调外机噪声的大幅度降低,压缩机的振动以及低频的噪声对于空调外机噪声的影响明显,需要引起关注。 相似文献
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实船试验研究了舱室空气噪声激励引起水下辐射噪声传递特性。采用模拟声源激励方式,建立舱室空气噪声激励引起水下辐射噪声实船试验方法。利用单输入/输出模型与传递函数,建立空气噪声至水下辐射噪声传递特性分析方法。通过实船声源激励试验,获取了空气噪声、水下辐射噪声及空气噪声至水下辐射噪声传递函数,分析给出空气噪声激励引起水下辐射噪声特征规律与传递特性,验证了实船传递特性试验与分析方法的可行性及有效性。研究结果表明,舱室空气噪声与水下辐射噪声呈线性关系,其传递关系表现为与频率相关的线性系统特征,50 Hz^5 kHz频段空气噪声至水下辐射噪声传递函数总体变化趋势呈现先增大后减小的特征规律。 相似文献
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电机轴承出现噪音也被称为电机噪音。电机的噪声由机械噪声、电磁噪声和通风噪声三部分组成,其中机械噪声的主要来源之一是轴承噪声,因此,控制电机的轴承噪声可以有效降低电机的整体噪声。轴承是电机的主要故障点之一。解决电机的轴承噪声可以降低电机的轴承故障,提高电机的整体质量水平。本文分析了影响电机轴承噪声的原因,介绍了问题的预防及解决措施。 相似文献
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城市高架轨道桥辐射噪声的计算与分析 总被引:3,自引:0,他引:3
为采取合适的噪声控制策略提供依据,预报城市高架轨道桥辐射噪声场很有必要.基于一个简化两维模型,考虑各种变化因素(两旁建筑物高度、间距等)的影响,应用边界元方法对进行了噪声场和频谱的计算预测,通过与实际测量数据的对比分析,结果表明:噪声的低频成分(<250Hz)主要由桥体结构振动辐射产生,而轮轨振动辐射是较高频(250~1000Hz)噪声的重要来源;低频噪声场上下明显强于两侧,而随频率的增高,声场混响特征增强.结论是:对于噪声不便于测试的高架桥这样大型结构,边界元方法能够有效预报噪声场,高架桥两侧声屏障可以取得5-10分贝的隔声效果,为防止上部出现噪声过大的情况两侧建筑物需要适当的高度/距离比. 相似文献
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针对造船厂船台生产作业噪声治理及降噪效果预测难的问题,提出船台噪声的治理方法。以某造船厂船台噪声治理为例,结合某造船厂船台噪声治理实例,提出船台噪声的治理方法,并针对其噪声特点,对噪声源进行建模,预测了主要治理措施的降噪效果。结果表明,造船厂船台生产作业噪声需从声源、声传播途径及生产作业管理等多方面进行综合治理;除降噪效果外,声屏障的设置还需考虑施工可行性、社会因素以及经济性等实际情况;对于船台生产作业噪声等分布范围广、密度大、垂向位置高的声源的模拟预测,需根据声源实际工况进行针对性建模。研究可为船台生产作业噪声等类似噪声源的噪声治理和预测提供参考。 相似文献
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《IEEE transactions on instrumentation and measurement》1996,45(6):935-941
The noise performance of an electronic quadrature phase-detection system for interferometric optical fiber sensors is presented. Three noise sources are discussed in this work, namely, synchronous detection-circuit noise, phase-perturbation noise; and additive amplitude noise. We determined the output signal-to-noise ratio (SNR) experimentally as a function of input phase power for each of the three noise sources. For uncorrelated synchronous detection-circuit noise the output SNR increases monotonically with input phase power. For correlated noise the output SNR has distinct peaks due to noise cancellation. System performance is limited by uncorrelated detection-circuit noise which exhibits a threshold behavior in output SNR at a phase shift of 25 mrad/Hz½. The phase noise has a more conventional behavior in the sense that SNR gain occurs only at the expense of dynamic performance. Uncorrelated amplitude noise also displays noise cancellation at certain discrete values of input phase, as is the case for correlated synchronous detection-circuit noise. System insensitivity to correlated light-source amplitude noise is evident from the fact that the output SNR is more than 30 dB higher than the input SNR 相似文献
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Noise of piezoelectric accelerometer with integral FET amplifier 总被引:1,自引:0,他引:1
Since significant progress has been achieved in the development of low-noise piezoelectric (PE) accelerometers with integral FET amplifiers, detailed noise analysis of the system PE transducer-FET amplifier, and obtaining the engineering formula for its noise floor has become vital. As a result of this analysis, the formula for the noise floor of PE accelerometers in terms of acceleration spectral density is obtained at wide frequency band. Noise floor of the low-noise PE accelerometer comprising low-noise JFET charge amplifiers with some particular parameters of the PE transducer and the JFET amplifier was measured. The theoretical and experimental curves of the PE accelerometer's noise floor have a good correlation with each other at frequencies from 1 Hz to 10 kHz. The contribution of the different noise sources to the overall noise floor is shown. Those noise sources include the mechanical-thermal noise and electrical-thermal noise of the PE transducer and all main noise sources of FET amplifiers: the thermal noise voltage of the FET biasing resistor, the thermal noise of the series resistor between the PE transducer and the gate of the FET, the channel thermal noise voltage, the 1/f noise voltage, and the shot noise current in the gate circuit. At low frequencies, the f/spl les/50 Hz noise floor is determined mainly by the FET biasing resistor's thermal noise and the PE transducer's electrical-thermal noise. At frequencies from about 50 Hz to about 1 kHz, the contribution of the PE transducer's electrical-thermal noise dominates over the amplifier's noise sources by a factor of less than 2. At frequencies above 1 kHz, noise floor is determined mainly by the JFET channel thermal noise and the PE transducer's electrical-thermal noise. 相似文献
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交通噪声是造成高校环境噪声超标的主要因素,尤其对城市道路下穿校园的新校区影响更大。运用噪声预测方法对在建的安徽理工大学新校区进行噪声预测评估,为其环境规划提供相应的依据和技术支持。通过测量统计校园周围道路不同类型的机动车流量数据,结合测量已有道路的交通噪声,利用Cadna/A噪声预测软件,建立新校区交通噪声模型,计算并绘制噪声网格分布图,并提出相应噪声控制措施。结果表明,通过采取在校园四周增加围墙,并在南北下穿城市道路旁设置声屏障等措施后,可以改善校园声环境,使其达到国家I类地区噪声规定标准。 相似文献