Article(id=1242117244579287067, tenantId=1146029695717560320, journalId=1146031591421210625, issueId=1242117211490419171, articleNumber=null, orderNo=null, doi=null, pmid=null, cstr=null, oa=null, hot=null, price=null, onlineType=0, articleFormat=0, articleType=null, articleTypeStr=null, receivedDate=1246377600000, receivedDateStr=2009-07-01, revisedDate=1253548800000, revisedDateStr=2009-09-22, acceptedDate=null, acceptedDateStr=null, onlineDate=1254067200000, onlineDateStr=2009-09-28, pubDate=1254067200000, pubDateStr=2009-09-28, doiRegisterDate=null, doiRegisterDateStr=null, onlineIssueDate=1254067200000, onlineIssueDateStr=2009-09-28, onlineJustAcceptDate=null, onlineJustAcceptDateStr=null, onlineFirstDate=null, onlineFirstDateStr=null, sourceXml=null, magXml=null, createTime=1774073428526, creator=sys-migrate, updateTime=1774073428526, updator=sys-migrate, issue=Issue{id=1242117211490419171, tenantId=1146029695717560320, journalId=1146031591421210625, year='2009', volume='27', issue='0918', pageStart='3', pageEnd='140', issueExtLink='null', onlineDate='null', pubDate='1254067200000', pubDateStr='2009-09-28', beforeIssueId=null, nextIssueId=null, price=null, status=1, issueComplete=1, articleOrder=3, issueType=-1, specialIssue=null, createTime=1774073420636, creator='sys-migrate', updateTime=1774073420636, updator='sys-migrate', preIssue=null, nextIssue=null, articleTotal=null, ext=null, issueFiles=null, downloadFileDto=null}, startPage=47, endPage=54, ext={EN=ArticleExt(id=1242117248786174013, articleId=1242117244579287067, tenantId=1146029695717560320, journalId=1146031591421210625, language=EN, title=Experimental Study on the Internal Flow on Air-modulated Speaker, columnId=1242116080374710456, journalTitle=Science & Technology Review, columnName=Articles, runingTitle=null, highlight=null, articleAbstract=The Air-Modulated Speaker (AMS) is one of the most popular high-power acoustic sources. High intensity sound waves are generated by the modulation of high speed air stream. Although there should be a close relationship between unsteady flow and acoustic source formation from the aero-acoustic point of view, few studies available concerning the internal flow evolvement inside the source. The velocity fields of 2D AMS steady model were obtained utilizing Particle Image Velocimetry (PIV). Static pressure measurements of unsteady internal flow were recorded by the flow induced sound monitoring system. Dominant steady flow characteristics were observed including pressure recovery, flow separation on the out wall and alternate appearance of low and high pressure area on the internal wall. Experimental results in the sound energy conversion process show that pressure distribution variation is related to the modulate frequency. The frequency response of the source is affected by many factors such as chamber pressure, input signal strength and some geometry sizes. Flow near the nozzle exit has certain influence on the voice coil vibration. Peak value of the frequency response is between 0.5 and 1 kHz. When the drive current is lower than 10 A, SPL output of AMS increases with the chamber pressure and amplitude of the drive signal. Width of nozzle exit and vocal tract inlet also have evident effects on the performance of AMS. In order to attain a higher SPL value, the acoustic source has to work in the full modulation condition by the proper adjustment of nozzle parameters, and small inlet width for vocal tract is also advantagious. Harmonic components in the distorted pressure are obvious in the source generation zone after the monochromatic modulation. The spectral composition of the distorted signal in the internal flow is coincident with the sound signal in the far field under the same working condition., authors=null, authorsList=null, authorCompany=null, correspAuthors=null, authorNote=null, correspAuthorsNote=null, copyrightStatement=null, copyrightOwner=null, extLink=null, articleAbsUrl=null, sourceXml=null, magXml=null, pdfUrl=null, pdf=u3huHdKLwUE01VcSWvvjFA==, pdfFileSize=890673, pdfExtLink=null, richHtmlUrl=null, mobilePdfUrl=null, reviewReport=null, pdfFirstPage=null, abstractGraph=null, abstractGraphContent=null, abstractVideo=null, citation=null, cebUrl=null, magXmlContent=null, mapNumber=null, fund=null), CN=ArticleExt(id=1242117247951503983, articleId=1242117244579287067, tenantId=1146029695717560320, journalId=1146031591421210625, language=CN, title=调制气流声源流场声场特性的实验研究, columnId=1146540929516700224, journalTitle=科技导报, columnName=研究论文, runingTitle=null, highlight=null, articleAbstract=已有大功率调制气流声源的实验集中于声场的测量，但对与声场特性密切相关的声源内部流场的演化过程研究较少。本文设计了稳态流场粒子图像测速（PIV）实验系统和流动致声单点测试系统，并分别用于内流场稳态和瞬态流动特性的研究。稳态流场实验结果中，喉道内呈减速增压流动，外壁面流动分离和近壁面高低压区域交替成为高气室压力下声源稳态流场的重要特征。流场扰动致声过程的测量数据表明，调制频率对内流场分布的变化有显著影响，强声波产生的频率相关性受气室压力、激励信号强度和声源几何参数等多种因素共同作用。气路系统的流动对调制部件的振动过程有一定影响，所测声源频率响应峰值位于0.5～1 kHz。激励电流低于10 A时，声压级输出随着气室压力和激励信号强度的增加而增加。喷口出口和喉道入口宽度对于声源性能也有明显的影响。从提高声源输出声压级角度，实际应用中应根据加载激励信号选择合适的喷口参数使声源工作于满调制状态，同时适当减小喉道入口宽度。单频调制的声源产生过程伴有谐波分量，非均匀流动中传递压力扰动的强度随管道截面积的增大而降低，压力扰动量级和成分与所测量声信号间存在密切联系。, authors=赵云¹,曾新吾², authorsList=赵云;曾新吾, authorCompany=1.国防科技大学理学院2. 国防科技大学光电科学与工理学院, correspAuthors=null, authorNote=null, correspAuthorsNote=曾新吾, copyrightStatement=null, copyrightOwner=null, extLink=null, articleAbsUrl=null, sourceXml=null, magXml=null, pdfUrl=null, pdf=gceqz3VNEt2VOClc9RfFgA==, pdfFileSize=890673, pdfExtLink=null, richHtmlUrl=null, mobilePdfUrl=null, reviewReport=null, pdfFirstPage=null, abstractGraph=null, abstractGraphContent=null, abstractVideo=null, citation=null, 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