- 马大猷
<正>We have a long history of acoustical investigation in China.The earliest record of acousticaltheory was found in writings of the sixth century B.C.,and legend put it much earlier.Acousticalphenomena were observed and discussed through the history.During the first half of this century,however,acoustics,like other branches of sciences,was left far behind,owing to the feudal-reactionaryrule prevailed in China.Only after the national liberation in 1949,the research in acoustics,boththeoretical and experimental,revived.A relatively strong research force was gradually formed,andmore and more important contributions were made in support of the socialistic reconstruction in China.The growth of the acoustical community,its academic activities and main contributions are reviewedin this article.
1986年02期 109-122页 [查看摘要][在线阅读][下载 5122k] [阅读次数：2 ] |[下载次数：37 ] |[引用频次：0 ] - 赵松龄
<正>In this papet,an improved theory about propagation of sound in highly concentrated suspensionsis elaborated.The effects of multiple scattering among suspended particles are taken into accountnot only for compressional wave but also for thermal wave and Viscosity wave.Supposing that thewavelength of scattered compressional wave is much larger than the diameter of suspended particles,we have found out the sound field near a particular particle produced by the thermal wave and viscouswave scattered from other particles by introducing proper statistical hypotheses.Hence,the rigoroussolutions can be obtained by means of the boundary conditions of the particle.The formulas forcalculating the effective density and effective bulk modulus of suspensions are derived in the paper.For two typical concentrated suspensions,namely,coal slurry and soil slurry,numerical results arecalculated and discussed.
1986年02期 123-136页 [查看摘要][在线阅读][下载 436k] [阅读次数：1 ] |[下载次数：16 ] |[引用频次：0 ] - 徐俊华
,兰军
<正>The influence of baffle on horizontal directivity and the frequency response of elements is analysedin detail in this paper.Some formulas of calculating the received response and the horizontal directi-vity of the cylindrical(arc)array are given.The influence of parameters of arrays on the performanceof the array is discussed.A comparison between the theoretical values and a part of the experimentalresults is shown.
1986年02期 137-148页 [查看摘要][在线阅读][下载 395k] [阅读次数：1 ] |[下载次数：14 ] |[引用频次：1 ] - 任树初
<正>A solution of the impedance wedge diffraction problem has been given by Malyuzhinets in Ref.[1].The key to the problem is to seek the solution of Malyuzhinets functional equations.However,how to go about getting the solution of the functional equations is not given in Ref.[1].A detailedprocess to get the solution of the functional equations is provided by using the infinite product theoryin Ref.[2],in which,however,there exist some errors and indistinct places. In this paper,these errors in Ref.[2] are corrected and another simpler method to obtain thesolution of the functional equations is also provided for the purpose of comparison.
1986年02期 149-155页 [查看摘要][在线阅读][下载 185k] [阅读次数：1 ] |[下载次数：13 ] |[引用频次：0 ] - 朱维庆
<正>In this paper,we discussed the underwater sound reverberation of moving medium,which is anon-stationary stochastic process even after compensating its energy attenuation.Evolutionaryspectra is introduced,and the non-stationary properties are described by a non-stationary factor anda characteristic width.We assumed that the Doppler shift is a stationary normal process or a normaladditive process and obtained the evolutionary spectra.After compensating the energy attenuation,a non-stationary sound reverberation can be expressed as a product of a deterministic time functionand a stationary stochastic function.The bi-hump in power spectrum is due to the non-stationarityand the non-homogeneity of the medium motion.When we use the estimation ν.i.e.the meanDoppler shift of a stationary process to estimate the mean Doppler shift of a non-stationary rever-beration process,the estimation ν is a biased one.
1986年02期 156-165页 [查看摘要][在线阅读][下载 358k] [阅读次数：1 ] |[下载次数：29 ] |[引用频次：0 ] - 饶宇安
,杨琼华
,梁之安
<正>Acoustic compliance was measured and calculated on tympanograms taken from 171 otologicallynormal ears with the MEFM-Apparatus,the test frequency being 300 Hz.The averaged maximumcompliance was found to be 1.16 ml at zero ear-canal pressure(C_0),and 1.29 ml at the point wherepressure in the ear canal equaled that in the tympanic cavity(C_e).The range of relative compliancechange in the tympanogram was 0.65 ml in average.For the majority(96.1%)of the tested ears,pressure in the tympanic cavity did not exceed ±50 mm H_2O.A new term of compliance variation(CR=ΔC_(Δp)/ΔC_(200))is introduced as a measurable parameter to express the gradient of compliancechange.It is proposed to take ±50 and ±100 mm H_2O for Δp in routine compliance ratio measure-ment and comparison.Normal CR is approximately 0.5 when Δp is ±50 mm H_2O.
1986年02期 166-173页 [查看摘要][在线阅读][下载 310k] [阅读次数：1 ] |[下载次数：18 ] |[引用频次：0 ] - 蒋锦昌
,聂世芳
,刘莉君
,徐慕玲
,孙巍
,刘向群
,王强
<正>In C.atrata Fabr.the sounding organ is a miniaturized sound-producing apparatus with multiplexstructural combinations.Its song consists of amplitude modulated pulse trains,with repetition fre-quency at about 180 Hz.The measurable bandwith is 200—12500 Hz with the main peak at 5 kHzand a tuning sharpness(Q_3dB)of 2.2±0.4.The song is produced by vibrations of the tymbaldriven by alternating contractions of the tymbal muscles on both side.The functions of the tymbalchamber are to ameliouate the song waveform and tuning characteristics and to increase volume.The abdominal chamber further helps to improve timbre and to raise volume.The main functionof the abdominal cavity is to raise song output.The joint membrane shows obvious effects on ameliora-tion of timbre and tuning characteristics.The operculum and the mirror membrane only have alittle effect on volume regulation. The construction and the function of the cicada sounding organ may serve as some kind of biolog-ical prototype for sounding equipment des
1986年02期 174-184页 [查看摘要][在线阅读][下载 1824k] [阅读次数：1 ] |[下载次数：18 ] |[引用频次：0 ] - 王佐民
<正>Noise sourcesi n an axisymmetric jet are ocated mainly near the nozzle,and their strengthdecreases continually with increase of X/D.According to this theoretical result,a round baffle absorp-tion muffler has been designed and studied in our laboratory.The muffler reduces jet noise mainlyof frequencies higher than 1 kHz.It is advisable to let the front of the muffler have a length of about25D.The muffler can be used not only for an exhaust jet,but also for a working jet.
1986年02期 185-192页 [查看摘要][在线阅读][下载 205k] [阅读次数：1 ] |[下载次数：21 ] |[引用频次：1 ] - 周康源
<正>Investigation of the tomogram of a liquid cylinder in homogeneous scattering medium is described.A model has been made and experiments on some sorts of liquid cylinders have been done.An ex-pression is derived for the brightness funotion of the tomograms while STC(Sensitivity Time Control)is used.According to this expression,the experiments on som sorts of mediums with differentacoustic properties have been simulated by computer.The resulte enable us to estimate acousticproperties of a liquid cylinder from its tomogram.
1986年02期 193-200页 [查看摘要][在线阅读][下载 2201k] [阅读次数：2 ] |[下载次数：8 ] |[引用频次：0 ] - 吴昆裕
,张谦琳
,陈兆甲
,吴柏枚
<正>With the pulse-echo technique the ultrasonic attenuation of shear waves in amorphous PdSiAgalloy has been measured as a function of frequency and temperature.At room temperature an ap-proximate f-squared frequency dependence is obtained between 10 and 240 MHz.Below 150K,at fixed frequency there is a slow increase of attenuation with decreasing temperature and a smallultrasonic absorption peak at 35K.The linear dependence of the relative variation of the soundvelocity is observed from 35 to 300K;the temperature coefficient of sound velocity is—1.58×10~(-4)/K.Below 35K,the relative varation of the sound velocity begins to deviate from the linear dependence.
1986年02期 201-204页 [查看摘要][在线阅读][下载 125k] [阅读次数：2 ] |[下载次数：14 ] |[引用频次：0 ] -
<正>. Stereophonic TechniquesAn Anthology of Reprinted Articles on Stereophonic TechniquesEdited and with a preface by John M.EarglePrice: $27.00 members,$30.00 Non-members.Audio Engineering Society,Inc.,60 E.42nd St.,Rm.2520,New York,NY 10165-0075 USA.. Forthcoming Eventsl."Third Natlbnal Symposium on Ulrasonics" (NSU-Ⅲ)Sept.25th and 26th,1986 at NPL,New Delhi, India(Organised by Ultrasonic Societyof India and NPL)
1986年02期 205-206页 [查看摘要][在线阅读][下载 44k] [阅读次数：2 ] |[下载次数：9 ] |[引用频次：0 ] 下载本期数据