边界和指向性声源对虚拟声屏障性能的影响研究

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1、JIIIIIlUlIIIIIIIIIIIIIIIIIY2371569THESIS：SPECIALIZATION：笪!QQ坠墨!i曼璺i．△堡!iY星旦Qi墨星曼Q!墅苫Q!)POSTGRADUATE：监i＆垒QMENTOR：ABSTRACTAVirtualSoundBarriersystem(VSB)cancreateaquietzonebyusingactivecontr01method．ResearchonVSBismainlybasedontheassumptionoffreefieldandnlon

2、opolesecondarysources．ThisthesisinvestigatedVSBsystemsneararigidwallor、Ⅳimdirectionalsecondarysources．Furthermore，anewdrivingfunctionforsecondarysourcesinaVSBsystemisdeducedandusedinlocalthreedimensionalsoundreproduction．TheeffectsofarigidwallonaVSBsystema

3、reinvestigatedfirstly．ItisfoundthatwhenaVSBsystemisclosetoareflectivesurface，itsnoisereductionperfo咖ancefluctuatesaroundtheoneinfreefield．Therigidreflectivesurfacemakesthenoisereductionvaryperiodicallywiththeincreaseofthedistanceandtheperiodlengthisdemonst

4、ratedtobehalfwavelengthfornormalincidence．Whenthedistanceisevenandoddtimesofquarterwavelength，thenoisereductionbecomesminimumandmaximumrespectively．Thisiscausedbythesimilarityofthedistributionpaaernsbetweentheprimarysoundfieldandthecontrolsoundfield．Beside

5、s，Ahybridvirtualsoundbarriersystemwithanearbyreflectivesurfaceisproposedandit'sperformanceisdiscussed．AnewdrivingfunctionforsecondarysourcesinaVSBsystemisdeducedbyusingtheconceptionofcontinuoussources．Basedonit，aVSBsystemusingfixed—directivitysourcesandvar

6、iable-directivitysourcesisdiscussedandcomparedwiththatusingtheconventionalleastsquaremethod．Itisfoundthatthenoisereductionusingthedirectionalsourcesishigherthanthatusingthemonopolesourceswhentheleastsquaremethodisadopted．Thenoiseofcontinuoussourcesmethodis

7、higherthanthatofleastsquaremethodattheplacenearthecenterofVSBsystem，whileatthefarplacethenoiseofcontinuoussourcesmethodislower．Beingcomparedwiththemonopolesources，thedirectionalsourcescanlowertheinfluenceontheouterspaceofVSBsystemFinally，basedonthecontinuo

8、usSOurCeSconcept，anewmethodisproposedinlocalthreedimensionalsoundreproductionandthefeasibilityofthemethodisdemonstratedbyusingnumericalsimulations．Thedrivingfunctionforsoundsourcesisdeduced，whichdependsontheo