可调吸声频率微穿孔板结构设计

提出一种吸声性能可调节的微穿孔板结构设计方法。设计并制作可调吸声频率的微穿孔板结构,该结构采用机械式旋转机构来改变微穿孔板实际参与吸声的穿孔数,进而起到调节吸声频率的作用。结构以29 mm内径的阻抗管为参数控制指标,使用声电类比法预测了结构的吸声性能,利用仿真和试验来验证结构可调吸声频率机理的正确性。同时,通过对微穿孔板微孔的不均匀化设计,达到可调吸声频率范围更大的目的。结果表明:设计出的方法可得到吸声频率可调的微穿孔板结构;常规微孔均匀分布的微穿孔板结构的吸声频率可调节范围可达14.3%;针对微孔不均匀分布的微穿孔板结构,吸声频率可调范围拓宽至:450 Hz^1050 Hz。

介电弹性薄膜吸声体的可调频率试验分析

利用介电弹性薄膜的电致动特性,设计一种可调频率的吸声体结构。该结构由介电弹性薄膜与空气背腔组成,通过调节施加在薄膜上电压大小改变其内应力,从而可使得薄膜吸声体的固有频率与吸声系数峰值对应频率发生偏移。实验结果表明:介电弹性薄膜吸声体固有频率随电压升高而降低,吸声系数各个峰值对应频率随电压增大均向低频偏移;背腔主要影响吸声系数大小,但对吸声系数峰值对应频率影响很小。通过对比其吸声系数峰值与比较模态振型可知,只有平均位移大于零的模态振型才对吸声性能有贡献。

非织造多孔吸声材料的发展与研究现状

介绍非织造多孔吸声材料的特点及影响因素。阐述了多孔吸声材料的吸声机理和评价指标,介绍了非织造多孔吸声材料的特点和种类划分。结合前人的研究,分析了影响非织造多孔材料吸声性能的因素,并介绍了当前非织造多孔吸声材料的研究现状和发展趋势。

桉木多层穿孔吸声板的制备及吸声性能评价

采用桉木多层胶合板制备穿孔吸声板,探讨孔径、穿孔率、胶合板厚度等因素对其吸声性能的影响。结果表明:穿孔率和胶合板厚度对试板吸声性能的影响极显著,孔径无显著性影响;制备穿孔吸声板较优工艺为:孔径3 mm、穿孔率14%、板厚18 mm;在声波频率100~6 300 Hz范围内,穿孔吸声板的平均吸声系数为0.5,在1 700 Hz附近,穿孔吸声板吸声性能最好。

绿色建筑水泥基复合材料吸声性能探究

分析绿色建筑水泥基复合材料吸声性能检测方法,使用稻草秸秆、水泥、石膏制作绿色建筑水泥基复合材料,采用吸声性测试方法检测其吸声性能,并讨论稻草秸秆长度、材料制作密度、厚度、表面处理以及空隙率对材料吸声性能的干扰。试验结果表明:若想优化绿色建筑水泥基复合材料吸声性能,可选用31 mm的稻草秸秆纤维,作为绿色建筑水泥基复合材料的纤维材料;当绿色建筑水泥基复合材料吸声频率小于800 Hz区间时,材料吸声性能随着密度、厚度增大而显著提升;相同吸声频率中,绿色建筑水泥基复合材料空隙率越大,吸声性能越差;绿色建筑水泥基复合材料表面可采取去除表皮21%、穿透孔处理,以此优化其吸声性能;与同类复合材料相比,绿色建筑水泥基复合材料吸声性能最优。

Absorption of sulfur dioxide using membrane and enhancement of desorption with ultrasound

The absorption of sulfur dioxide in simulated flue gas by using liquid-containing membrane was investigated.The process of sulfur dioxide desorption from the absorbent of citrate solution was explored.The influence of the gas-phase,and the liquid-phase on absorption efficiency of sulfur dioxide and the influence of ultrasonic frequency,ultrasonic power and stirring speed on desorption efficiency of sulfur dioxide were examined.The results indicate that the absorption efficiency decreases with increasing flow velocity and sulfur dioxide content in gas-phase,and can be improved by increasing the concentration and the pH value of citrate solution.It is concluded that lower ultrasonic frequency results in a better degassing efficiency.The using of ultrasound in desorbing sulfur dioxide from citrate solution improves the desorbing efficiency in the some conditions,without changing the essence of chemical reaction.

The Influence of an Acoustic Field on the Bed Expansion of Fine Particles

Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied.The effects of sound pressure level,sound frequency and particle loading on the bed expansion were investigated.Experimental results showed that,bed expansion was good in presence of acoustic field of particular frequency.In addition,it was observed that in presence of acoustic field the bed collapses slowly.