英语翻译Standing waves most commonly occur in any regular enclosure which possesses at least one set of parallel walls.The criterion for the frequencies at which they may become established is related to the separation distance between parallel s

英语翻译Standing waves most commonly occur in any regular enclosure which possesses at least one set of parallel walls.The criterion for the frequencies at which they may become established is related to the separation distance between parallel s
英语翻译
Standing waves most commonly occur in any regular enclosure which possesses at least one set of parallel walls.The criterion for the frequencies at which they may become established is related to the separation distance between parallel surfaces by
公式：
where
n is the 1,2,3...
c is the velocity of sound propagation,m/s
d is the separation distance,m
fn is the nth harmonic frequency,Hz.
Note that the term n is included because harmonics of standing waves may occur at integer multiples of the fundamental.
This phenomenon is of particular importance in the transmission of vibrational energy through plates and bars,as well as in airborne sound transmission through limited spaces of regular geometry.In both situations,reflection relatively free of energy loss at the metal or room boundaries may occur,with a phase change of approximately 360 °.In practice,therefore,particular structures and spaces may tend to amplify acoustic energy at those frequencies where standing waves occur.Therefore,when designing noise control procedures,for example,enclosures,particular attention must be paid to preventing standing wave formation at frequencies given by the above formula,to prevent undue degradation in predicted attenuation performance.An alternative description used for resonance in solid materials is normal modes of vibration.
2.4 DECIBELS
The parameters typically used to describe sound have very wide ranges.Frequencies may change by an order of 10 4,sound power or intensity by 1016 ,and sound pressure by 10 8.To simplify the graphical and numerical expression of these quantities,they are represented by means of a logarithmic transformation.In the case of sound power,intensity,and pressure,this is achieved using the decibel scale.
Essentially,decibels are calculated by taking the logarithm of the ratio of the value of the parameter of interest to a fixed reference value of that parameter,and multiplying it by 10.The advantages of this are threefold:it avoids large exponents in representing the quantities; the human ear judges sounds according to the ratio of intensities,so that the subjective effect is reasonably approximated; and electrical engineers use decibels in evaluating electrical power and voltage,so that conversion of quantities and units at electroacoustic transducers is simplified.By convention,parameters are taken as "levels" when their units are expressed in decibels.
An acoustical source having a sound power of W watts is therefore said to have a sound power level PWL given by
公式：PWL = 10 log 14";ref dB

英语翻译Standing waves most commonly occur in any regular enclosure which possesses at least one set of parallel walls.The criterion for the frequencies at which they may become established is related to the separation distance between parallel s
最常发生在驻波任何正规的外壳,拥有至少一套平行墙.这个标准的频率在可能会使他们成为建立与分离距离平行表面
公式:
在
诺拉是1,2,3……
c是声传播的速度,米/秒
医生是分离的距离,m
新生力量是第n次谐波频率、赫兹.
注意,因为是驻波谐波的整数倍的可能的根本.
这种现象是特别重要的凝聚相中的振动能量通过板和酒吧,以及在空中声透射有限的空间的常规的几何形状.在这两种情况下,反射相对自由的能量损失的金属或房间的界限,有可能发生相变大约360°.在实践中,因此,特殊结构和空间可能倾向于在这些频率放大的能量在驻波发生.因此,在设计噪声控制程序,例如,围栏,必须特别注意防止驻波在频率上形成的上述公式,以防止不必要的退化预测消声性能.另一种描述用于谐振在固体物料正常模式的振动.
24分贝时,
这个参数通常用来形容很广的范围.声音频率可能改变一个10 4、声功率和强度的影响,并通过声音压1016十块八块.简化的图形和数字表达的数量,他们代表的对数变换.在这个案例的声功率、强度、和压力,这就要用到分贝.
从本质上讲,分贝计算以对数的参数的值,以一个固定的参考价值感兴趣的参数,它由10个甚至倍增.这是孤身一人的优势:它避免大的指数代表数量;人类的耳朵听起来照审判的比率,这样的强度是主观作用;电气工程师使用接近电源和评估分贝的电压,以便转换的量和单位在电声变换器的解析解.按照惯例,参数作为“水平”时,他们的单位均以分贝.
有一声来源的声功率W是瓦茨说:“有一声功率级PWL给出
公式:PWL = 10日志14”;参考分贝

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早说啊 自己看着扯淡就好了