排序方式: 共有38条查询结果,搜索用时 15 毫秒
2.
The acoustical quality of an ordinary hall,namely the reverberation time and the spatial nonuni-formity of sound pressure level in audience area,was simulated on a microcomputer.Comparisonbetween calculation,measurement and simulation of reverberation time shows that the reverberationtime from simulation is closer to measurement than from calculation,if the absorption of the audience isproperly chosen,in the frequency range from l25 to 4000 Hz;the average deviation is less than 10%.For the spatial nonuniformity of sound pressure level,there is a good correspondency botween thesimulation and the measurement.In addition,some details in simulation were discussed. 相似文献
3.
阻塞喷注的冲击噪声 总被引:7,自引:0,他引:7
冲击噪声是阻塞喷注噪声的重要部份。我们对它的声场和频谱作了详细的实验测量,由于采用外差分析技术,冲击噪声的离散谱和宽带谱可同时记录。实验表明,声场和频谱与驻压比的关系很复杂,但在与喷注垂直的方向上,距喷口1米处的总声压级,如驻压比在3到8.5之间,约为97+20logd分贝,基本不受驻压变化的影响,其中d是喷口直径,以毫米计。进一步又给出了全部驻压比范围内的总声压级的表达式。宽带谱在驻压比为2.5到7之间,离散谱在5到7之间最突出,驻压比小于2或大于8.5,阻塞喷注噪声则主要是湍流噪声。本文还给出了计算离散谱频率和宽带谱峰频的新公式;对实验中观察到的离散谱的非谐频成份,也作了解释。在喷注上游方向,观察到阻塞喷注噪声频谱具有一个或几个凹陷部份,表明在这些频率范围存在干涉现象,可能是湍流噪声与宽带冲击噪声之间的干涉现象,文中说明了这种干涉的可能性。 相似文献
4.
5.
The investigation on the characteristics of diameter-expanded silencers was carried out experi-mentally and some results were obtained:1.silencers are effective only in a limited plenum chamber(stagnation)pressure range and have maximum of noisc reduction when the condition(P_0/P_1,v)/(d_A~1/d_S~2)=0.81 is fulfilled;2.silencers also have certain expansion selection,i.e.d_S/d_A must belarger than 1.5 and smaller than 2.5;3.the length of silencers has no marked effect on their charac-teristics in the effective pressure range;4.the efflux noise of silencers in the effective pressure rangecan be calculated according to the pressure dependence of turbulent noise and the correction to theexpansion ratio.Finally,two notable phenomena,which are valuable for further study,are putforward. 相似文献
6.
大爆炸是研究宇宙起源的现代科学命题之一。不可想象的是,直到最近,除了题目外,研究尚缺少任何有关声学的内容。大爆炸是1950年由Fred Hoyle命名的,他开始时的研究也与声波无关,仅与宇宙早期膨胀的"爆炸"特性有关。现在几十年过去了,关于宇宙起源的许多其它特性得到了广泛的研究,甚 相似文献
7.
8.
Formulae for calculating the transmission loss and the specific acoustic impedance of sandwichpanels are put forward by linear fitting the experimental data of various references and ours. 相似文献
9.
高压阻塞喷注的湍流噪声 总被引:6,自引:0,他引:6
过去曾求得驻点压力(表压)在0.01到10大气压适用的喷注噪声的压力关系。现在将实验扩展到100大气压过热水蒸汽,发现低压时的关系仍然适用,不过由于喷注气体不同,此时多一个附加项20log(M0/M),M0和M分别是空气和喷注气体的分子量;喷注温度则几乎无影响。于是,在与喷注方向垂直,距离喷口1米处的A声级就成为${L_A} = 80 + 20\\log \\frac{D}{{{D_0}}} + 20\\log \\frac{{{M_0}}}{M} + 10\\log \\frac{{{{(P - {P_0})}^4}}}{{{P_0}^2{{(P - 0.5{P_0})}^2}}} + 10\\log \\left[ {\\frac{2}{\\pi }\\left( {{{\\tan }^{ - 1}}{x_A} - \\frac{{{x_A}}}{{1 + {x_A}^2}}} \\right)} \\right]$式中D为喷口直径(mm),D0为1mm, P和 P0分别为喷注驻压和环境大气绝对压力,在阻塞时xA=0.165D/D0实验证明在较大的温度和压力范围,噪声频谱无甚差别。管道内的扰动可使噪声级提高1-6dBA,对此本文作了理论分析。低压时使 用的小孔消声器在高压下仍然有效,但应注意其特有的关系. 相似文献
10.