Neural control of vocalization: Respiratory and emotional influences

Previous research has shown that a region of the midbrain, the periaqueductal gray matter (PAG), is critical for vocalization. In this review, we describe the results of previous investigations in which we sought to find out how PAG neurons integrate the activity and precise timing of respiratory, laryngeal, and oral muscle activity for natural-sounding vocalization using the technique of excitatory amino acid microinjections in cats. In these studies, all surgical procedures were carried out under deep anaesthesia. In the precollicular decerebrate cat two general types of vocalization, classified as voiced and unvoiced, could be evoked by exciting neurons in the lateral part of the intermediate part of the PAG. The patterns of evoked electromyographic activity were strikingly similar to previously reported patterns of human muscle activity. Coordinated patterns of activity were evoked with just-threshold excitation leading to the conclusion that patterned muscle activity corresponding to the major categories of voiced and voiceless sound production are represented in the PAG. In a parallel series of human and animal experiments, we also determined that the speech and vocalization respiratory patterns are integrated and coordinated with afferent signals related to lung volume. These data have led to the proposal of a new hypothesis for the neural control of vocalization: that the PAG is a crucial brain site for mammalian voice production, not only in the production of emotional or involuntary sounds, but also as a generator of specific respiratory and laryngeal motor patterns essential for human speech and song     

瓦斯煤尘爆炸火焰光谱的实验研究

本文概述了瓦斯煤尘爆炸火焰光谱实验研究的重要性,我们在弱爆炸和探测器小视场角的条件下,利用自己研制的多波道仪,在一端开口的Φ200cm×2900cm大型管道里,得到了CH4、空气和煤尘的混合物在不同状态下,特征波长λ等于0.8875、1.000、1.505、2.801和4.346微米(μ)的绝对辐射强度及其有关的变化规律,对结果进行了分析讨论,并与国外实验结果进行了对比,根据测量λ=4.346μ绝对辐射强度和我们选择的黑体辐射模型,获得了爆炸火焰的温度,该项研究不仅在工业中具有重要意义,而且对燃烧和化学动力学的研究也具有参考价值。     

Comparison on the mixture rules of sound velocities used in characterizing biomedium components

In this paper, several mixtrue rules of sound velocity and their useful ness in characterizing the components of biomedium are analysed. It is pointed out that for characterizing the components of biomedium, the rules are compatible with each other under certain conditions, and the errors between each rule and real sound velocity are diffferent. It concludes that there is no general rule suitable for various media among above mentioned rules.     

Insertion loss of sound waves through composite acoustic window materials

This study evaluated the insertion loss of sound waves through composite acoustic window materials for sonar dome applications, and examined the influence of dome shape on the sonar performance. The insertion loss of sound waves through acoustic window materials was experimentally measured as a function of frequency at normal incidence. The insertion loss was also theoretically estimated with three- and four-medium layer models. The theoretical estimation of insertion loss showed good agreement with the experimental measurements. The insertion loss was also measured as a function of angle of incidence. The characteristics of longitudinal and converted shear waves were observed at various angles of incidence. This study will be useful to select acoustic window materials with the appropriate acoustic characteristics for practical sonar dome applications.     

Propagation of sound waves through a spatially homogeneous but smoothly time-dependent medium

The propagation of sound through a spatially homogeneous but non-stationary medium is investigated within the framework of fluid dynamics. For a non-vortical fluid, especially, a generalized wave equation is derived for the (scalar) potential of the fluid velocity distribution in dependence of the equilibrium mass density of the fluid and the sound wave velocity. A solution of this equation for a finite   transition period τ$\tau$ is determined in terms of the hypergeometric function for a phenomenologically realistic, sigmoidal change of the mass density and sound wave velocity. Using this solution, it is shown that the energy flux of the sound wave is not conserved but increases always   for the propagation through a non-stationary medium, independent of whether the equilibrium mass density is increased or decreased. It is found, moreover, that this amplification of the transmitted wave arises from an energy exchange with the medium and that its flux is equal to the (total) flux of the incident and the reflected wave. An interpretation of the reflected wave as a propagation of sound backward in time is given in close analogy to Feynman and Stueckelberg for the propagation of anti-particles. The reflection and transmission coefficients of sound propagating through a non-stationary medium is analyzed in more detail for hypersonic waves with transition periods τ$\tau$ between 15 and 200 ps as well as the transformation of infrasound waves in non-stationary oceans.     

Suppression of slag foaming by a sound wave

The aim of this work was to study the effects of sound frequency, sound intensity and viscosity of slag on the slag foaming rate and the steady-state foam height. Experiments were carried out using two slags (BaO–B₂O₃) melted at a temperature of 1223 or 1273 K, as well as water–glycerin solutions at room temperature. Low frequency sound waves (<1.3 kHz) are found to be more effective in the slag foaming suppression than high frequency waves (1.3–12 kHz). The steady-state foam height decreases abruptly when the sound pressure reaches a threshold value that depends on sound frequency and liquid viscosity. The results can be explained in terms of enhancing the rates of liquid drainage and film rupture induced by sound.     

Development of a highway traffic noise prediction model that considers various road surface types

A highway traffic noise prediction model has been developed for environmental assessment in South Korea. The model is based on an outdoor sound propagation method and is fully compliant with ISO 9613 and the sound power level (PWL) estimation for a road segment, as suggested in the ASJ Model-1998 that is based on PWLs. Due to that model’s selection of two pavement types, such as asphalt or concrete pavement, an unacceptable traffic noise prediction is made in cases where the road surface is different from that on which the model is based. In order to address this problem, several road surface types are categorized, and the PWL of each surface type is determined and modeled by measuring the noise levels obtained from newly developed methods. An evaluation of the traffic noise prediction model using field measurements finds good agreement between predicted and measured noise levels.     

A simple impulse sound source for measurements in room acoustics

This paper deals with the construction and characteristics of a specially designed wooden clapper intended to operate as an impulse sound source for measurements in rooms. It is to be used as an alternative impulse sound source for experimental estimations of impulse responses of rooms located at remote and specific places where none of the standard sound sources - an omnidirectional loudspeaker system, etc. - can be used. The paper describes the spectral characteristics and directivity of the clapper impulse. Its features are compared with other impulse sources.     

A pilot study on improving the absorptivity of a thick microperforated panel absorber

Microperforated panel (MPP) absorbers are promising as a basis for the next-generation of sound absorbing materials. MPPs are typically made of a thin metal or plastic panel. However, thin limp panels are generally not suitable as an interior finish of room walls because they do not have sufficient strength, which prevents practical application of MPPs as an interior finish of room walls. In order to overcome the lack of appropriate strength required for room walls, it is possible to make an MPP out of a thick panel. However, thick MPPs are usually not efficient because the resistance and/or reactance become too high. In this study, trial production of thick MPPs and measurement of their normal absorption coefficients were carried out. Results show that efficient absorption can be given with a thick MPP by using a tapered perforation.     

Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers

Starting from the exact acoustic scattering from a sphere immersed in an ideal fluid and centered along the propagation axis of a standing or quasi-standing zero-order Bessel beam, explicit partial-wave representations for the radiation force are derived. A standing or a quasi-standing acoustic field is the result of propagating two equal or unequal amplitude zero-order Bessel beams, respectively, along the same axis but in opposite sense. The Bessel beam is characterized by the half-cone angle β of its plane wave components, such that β = 0 represents a plane wave. It is assumed here that the half-cone angle β for each of the counter-propagating acoustic Bessel beams is equal. Fluid, elastic and viscoelastic spheres immersed in water are treated as examples. Results indicate the capability of manipulating spherical targets based on their mechanical and acoustical properties. This condition provides an impetus for further designing acoustic tweezers operating with standing or quasi-standing Bessel acoustic waves. Potential applications include particle manipulation in micro-fluidic lab-on-chips as well as in reduced gravity environments.