基于声学传感器的可调式电子戒鼾器的设计

论述了基于声学传感器的电子戒鼾器的工作原理,介绍了设计等相关电路,给出基于声学传感器的电子戒鼾器的调试数据。调试结果表明,设计的电子戒鼾器的电路合理、可靠且具有不同的人可根据自身的情况来调节电子戒鼾器的输出电压功能。经临床试验,戒鼾效果良好,研制的电子戒鼾器具有很好的市场应用前景。     

水下隔声材料的声学优化设计

将约束优化理论引入声学设计领域,以带结构的水下隔声层为分析对象,阐述了序列二次规划算法用于声学优化设计的基本过程和关键步骤。通过对带结构的水下隔声层所用橡胶材料参数的优化设计,为水下隔声橡胶的参数设计提供了设计的基本方向,对于提高其水下隔声性能具有重要意义。     

A study of sound intensity control for active noise barriers

Active noise control systems have been applied to increase the insertion loss of noise barriers where the squared sound pressure or the total acoustic energy density is used as the cost function in previous works. The absolute value of the mean active sound intensity is chosen as the cost function to obtain extra sound insertion loss in the dark area of a hybrid active noise barrier system in this note. The strategy of minimizing the near-field sound intensity at discrete locations along the edge of the passive barrier is shown to be able to provide better far-field noise reduction than that of minimizing the squared sound pressure control. Both numerical simulations and off-line experiments are carried out with a three-channel demonstration system, where the locations of the secondary sources and the error sensors are optimized and comparisons are made between the extra sound pressure attenuation of the sound intensity control and that of the squared sound pressure control.     

气体火焰驻波演示实验的理论分析

对通过声场使可燃气体产生火焰驻波的波形进行研究,得出火焰驻波在波节处(固定反射端)出现火焰,在波腹处几乎不出现火焰的结论,理论分析与实验观测相符.     

简谈空气中的声速与温度关系

讨论了驻波法测空气中声速的实验,分别用相位比较法和李萨如图法来确定超声波波长.在不同温度条件下测量了声速并与理论值进行比较,实验结果显示测量温度接近室温时实验值与理论值基本一致,测量温度与室温相差较大时实验值与理论值偏差较大.     

立足之本和增值之道——浅谈专业功放设计和配置思路

"可靠性"、"稳定性"及"守法"是专业功放开发生产的立足之本。提高专业功放性能必须围绕要放大的"信源"信号和要驱动的扬声器系统的需求来展开,最终为人们的听觉服务。把放大器作为音响系统的一部分,从电声学的角度来提高功放性能,是专业功放设计和配置的增值之道。不论专业功放配置使用在何种音响系统,从可靠性观点考核,音响系统的峰值功率储备应避开"7dB陷阱",最低12dB,最好大于等于14dB。     

Density, Viscosity, Refractive Index, and Speed of Sound in Binary Mixtures of Pyridine and 1-Alkanols (C6, C7, C8, C10) at 303.15 K

The densities (ρ), viscosities (η), refractive indices (nD), and speeds of sound (u), of binary mixtures of pyridine with 1-hexanol, 1-heptanol, 1-octanol and 1-decanol, including those of pure liquids, were measured over the entire composition range at 303.15 K and atmospheric pressure. From these experimental data, the values of excess molar volumes (VE), deviations in isentropic compressibilities (Δks), viscosities (Δh), molar refractions (ΔRm), apparent and partial molar volumes (Vf,2 and ), apparent and partial molar compressibilities (Kf,2 and ), of alkanols in pyridine and their corresponding deviations (ΔV and ΔK) were calculated. The variations of these parameters with composition of the mixtures suggest that the strength of interactions in these mixtures follow the order: 1-hexanol＞1-heptanol＞1-octanol＞1-decanol. All the excess and deviation functions were fitted to Redlich-Kister polynomial equation to determine the fitting coefficients and the standard deviations.     

Intellectual Family Life of Sound and Photoelectricity——Exploring Revolutionary Way of Family Life

Professional amusement family is turning to family′s amusement in Europe. The intellectual family system of sound and photoelectricity and its principle are introduced. According to a case, the application and implement of the system are discussed.     

Performance Evaluation and Effectiveness of the Reverberation Room

This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards (NIS) according to the related international standards. The evaluation aims at examining the room performance and exploring its effectiveness in the frequency range from 125 Hz to 10000 Hz according to the international standard requirements. The room, which was designed and built several years ago, is an irregular rectangular shape free from diffusers. Its volume is about 158.84 m³, which meets the requirement of the ISO 354 standard L_max < 1.9V^1/3. Cut-off frequencies of one and one-third octave are 63 Hz and 100 Hz respectively; however Schroder frequency is 400 Hz. Calculations of cut-off frequency and modal density showed adequate modes that give acceptable uniformity starting comfortably from frequency of 125 Hz. The room has a reverberation time that is suitable for its size over the frequency range of interest. The room sound absorption surface area and its sound absorption coefficient satisfy the criteria given in ISO 3741 and ISO 354. There is an accepted diffuse sound field inside the room due to the standard deviation of measured sound level, which is less than 1.5 dB over all the frequency range. The only exception was 125 Hz which may be due to a lack of diffusivity of the sound field at this frequency. The evaluation proves that the NIS reverberation room is in full agreement with the international standards, which in turns qualifies the room to host measurements inside without concerns.     

Ultrasound-assisted of alkali chloride separation using bulk ionic liquid membrane

An ultrasonic-assisted separation of alkali chloride (LiCl, NaCl, and KCl) salts have been carried out using of an hydrophobic ionic liquid membrane (ILM). The ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and tributyl phosphate mixture have been used as ILM. An ultrasonic probe with different frequencies (25, 100, and 250) kHz have been applied as source of ultrasound generator with different times of sonication (2, 5, and 10) min in three phases system containing feed, ILM, and receiver in osmotic U-shaped tube. Also, 250, 500, and 1000 ppm of the feed (alkali chloride) concentration have been used to separate. The frequency of 250 kHz with higher sonication time provides optimum condition for separation of LiCl with lower feed concentration. The thermodynamic properties such as density and speed of sound and the related thermodynamic properties have been calculated to optimize ILM composition (x_IL = 0.45) for ultrasound-separation.