共查询到18条相似文献,搜索用时 62 毫秒
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二、“现代”大气声学1.重力和科里奥利(Coriolis)力对声传播的影响(1)声重力波和内重力波重力场对寻常声波(包括可听声和频率较高的次声,当然更包括超声,但因后者在空气中衰减太快,不能成为大气声学研究对象)的影响完全可以忽略,但当频率低到一定程度时就必须考虑这种影响了.声波中的运动加速度与频率的平方成正比,对于寻常声波,这一加速度的数值远比重力加速度g大.但当频率的数量级约为g/c时,这两个加速度就属于同数量级的了.实际上,因重力作用,大气密度随高度增加而减小.例如,对于频率为g/c0.029Hz的声波,其波… 相似文献
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为探究宗教信仰是否影响人对宗教建筑广场声景的心理感受,该研究基于声景生态学对声景元素的分类,通过模糊层次综合评价法构建由地球物理声、生物声和人工声3个准则层元素和16个指标层元素组成的宗教建筑广场声景评价体系。以哈尔滨市的5个教堂为例,对有宗教信仰和无宗教信仰的游客和居民进行调查。结果表明:有无宗教信仰的受访者对宗教建筑广场声景总体评价的结果分别为很好和较好;在准则层中,地球物理声的评价结果皆为较好,生物声的评价结果皆在一般及以上,而人工声则与生物声相反;有宗教信仰的受访者对除昆虫鸣叫声外的生物声景的评价等级均比无宗教信仰的受访者高一级,对广场广播声的评价等级比无宗教信仰的受访者低一级,其余指标的评价结果均一致。评价结果符合实际,为今后宗教建筑广场声景评价研究提供了有效方法。 相似文献
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The acoustic and perceptive characteristics of discourse units, including clauses, simple sentences, compound sentences and paragraphs, were studied. The acoustic characteristics were based on the analysis of a speech corpus consisted of ten monologues. The Perceived Boundary Strength (PBS) of the monologues was labeled on a five-point scale by 25 participants. The main results are as follows: (1) There is a significant difference in the PBS of clauses (corresponding to intonational phrase), sentences (including simple sentences and compound sentences) and paragraphs. But the PBS of simple sentences and compound sentences is the same, and the pitch reset and pause are also not significantly different between these two kinds of boundaries. (2) The pitch-based cue used to distinguish clauses, sentences and paragraphs appears to be the difference between pre- and post-boundary syllables, but not simply the pitch value of either syllable alone. (3) Declination mainly occurs within intonational phrases, whereas there is no consistent global declination in sentences or in paragraphs. (4) Pauses are longer and more varied at the boundary of larger discourse units. Moreover, there is a significant positive correlation between pause duration and degree of pitch reset at clause boundaries, but not at sentence or paragraph boundaries. 相似文献
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We exploit theoretically a class of rectangular cylindrical devices for noise shielding by using acoustic metamateriais. The function of noise shielding is justified by both the far-field and near-field full-wave simulations based on the finite element method. The enlargement of equivalent acoustic scattering cross sections is revealed to be the physical mechanism for this function. This work makes it possible to design a window with both noise shielding and air flow. 相似文献
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本文介绍自W.C.Sabine以来100年厅堂声学的发展简史,包括室内声学理论,音指标与评价,声学测试方法,缩尺模型技术,计算机仿真技术及厅堂设计的发展,现状及关于今后研究方向的前瞻。 相似文献
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Open plan classrooms, where several class bases share the same space, have recently re-emerged in Australian primary schools. This study compared the acoustics of four different Kindergarten classrooms: an enclosed classroom with 25 students, a double classroom with 44 students, a linear fully open plan triple classroom with 91 students, and a semi-open plan K-6 classroom with 205 students. Ambient noise levels, intrusive noise levels, occupied background noise levels, and teacher’s speech levels were recorded during different activities. Room impulse responses using logarithmic sweeps were also recorded for different teaching scenarios. From these recordings, signal-to-noise ratios, speech transmission index scores, and reverberation times were calculated. The results revealed much higher intrusive noise levels in the two largest open plan classrooms, resulting in signal-to-noise ratios and speech transmission index scores to be well below those recommended in classrooms with students of this age. Additionally, occupied background noise levels in all classrooms were well above recommended levels. These results suggest noise in classrooms needs to be better controlled, and open plan classrooms are unlikely to be appropriate learning environments for young children due to their high intrusive noise levels. The impact of noise on children’s learning and teacher’s vocal health are discussed. 相似文献
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Ayman I. Madbouly Amin Y. Noaman Abdul Hamid M. Ragab Ahmed M. Khedra Ayman G. Fayoumi 《Applied Acoustics》2016
In this paper, a new classroom acoustics assessment model (CAAM) based on analytic hierarchy process (AHP) for enhancing speech intelligibility and learning quality is proposed. The model is based on five main criteria that affect the learning process and related to classrooms acoustical properties. These include classroom specifications, noise sources inside and outside the classroom, teaching style, and vocal effort. The priority and weights of these major criteria along with their alternatives are identified using the views of students, staff, education consultants, and expertise by using a developed questionnaire, and the AHP methodology. This model can be considered as a helpful framework enabling universities decision makers to take effective decisions on classroom acoustics treatment issues. It also provides colleges’ higher authorities the suitable guidelines that help for determining necessary requirements that help to raise the quality and efficiency of the educational environment; in order to reach an excellent learning environment; and hence increasing students learning outcomes. 相似文献
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In some cases an impulsive noise source such as a gunshot can be a preferred alternative when investigating building acoustics, including sound insulation measurements, when compared to conventional steady state noise sources. A gun equipped with blank cartridges is an impulsive noise source that is lightweight and small enough to be easily transported. The differences in the noise characteristics between individual cartridges for the same gun are usually small, so the impulsive source can be replicated to a high degree. This paper is focused on the practical application of the sound exposure levels produced by a gunshot with a known sound energy level in the rooms under investigation. In this way, the equipment and methods required by the conventional method are simplified significantly. Furthermore, reverberation times need not be measured, since the equivalent absorption area can be directly obtained from the measured sound exposure levels. Using Green’s theorem, the roles of the sound source and measuring microphone were exchanged, which simplified the determination of sound insulation as it was easier to change the position of the gun than the microphone. The results obtained using the impulsive noise source were in good agreement with those obtained using the conventional method. Above 100 Hz, their difference in any frequency band of interest was less than 1 dB. 相似文献