柔性材料振动吸声理论

出版时间：2010-1  出版社：西安交通大学出版社  作者：张新安  页数：171  

前言

　　The sound absorption material plays an important role in room acoustic and environmental noise control.In general.thetraditional sound absorption material is the porous material，perforated panel，plate and membrane material.British great classical physicist Lord Rayleigh put forward the micropore viscosity sound absorption theory of porous material more than100 years ago.Zwikker and Kosten made further development ofthe theory 50 years ago.Although the research has undergone formore than 100 years，a majority of the scientists still follow suchconcept，the pore space of the porous material and perforatedmaterial produces the viscous effect on the fluctuating air of thesound wave，with which the sound energy is converted into heatenergy.　　Whereas，the author discovered that the incident soundabsorption coefficient of the fibrous material related to thethickness of the air layer behind it.When the thickness of the airlayer is equal to 1／4 of the wavelength of the incident soundwave，the maximum value of the sound absorption will beproduced，when the thickness of the air layer is equal to 1／2 ofthe wavelength of the incident sound wave，the minimum value ofthe sound absorption will be produced.

内容概要

　　The sound absorption material plays an important role in room acoustic and environmental noise control.In general.thetraditional sound absorption material is the porous material，perforated panel，plate and membrane material.British great classical physicist Lord Rayleigh put forward the micropore viscosity sound absorption theory of porous material more than100 years ago.Zwikker and Kosten made further development ofthe theory 50 years ago.Although the research has undergone formore than 100 years，a majority of the scientists still follow suchconcept，the pore space of the porous material and perforatedmaterial produces the viscous effect on the fluctuating air of thesound wave，with which the sound energy is converted into heatenergy.

作者简介

　　Doctor Xin-an Zhang was born January1 963 He worn the mathematicaI competition prize ln 1 978 when he was a senior middle school student in Xianyang City.In 1 981 atthe age of 1 8.he graduated from Northwest Instituted of Textile Science and Technology，where he remained as a facuIty member and went On to earn his Masters degree in 1989.Since then.he was employed as the associate professor of Xian Polytechnic University Being welI acquainted and good sense of fibrous materials with the research achievements of physical p rope rties Of fibrous mate rialS.in 2004，he was taken in T0ngji University as the Ph D student to performed the research in sound absorption properties of fibrous materials　　When not teaching and writing，Zhang PU rSUes hiS inte rest in ACUPUnctU re me ridians and exe rcises Taiji Which he believes can prolong Iife and anti-decease.

书籍目录

PrefaceChapter 1 Properties and Testing Methods of Sound AbsorptionMaterials1.1 Properties of Sound Absorption Materials1.1.1 Porous Absorptive Materials1.1.2 Resonant or Reactive Absorbers1.2 Measurement of Sound Absorption Materials1.2.1 Measurement of Acoustic Parameters1.2.2 Measurement Method and Apparatus of Air Permeability and Yield Strength of Fiber LayerChapter 2 Introduction of Conventional Sound Absorption Theories2.1 Sound Transmission of Porous Materials2.1.1 Sound Transmission in the Round Pipe and Narrow Slit2.1.2 Porous Sound Absorption Materials2.1.3 Porous Sound Absorption Materials in Several Specific Cases2.2 Sound Absorption in Diaphragmatic AbsorberChapter 3 An Empirical Formula for Sound Absorption of Fibrous Materials3.1 Introduction3.2 Sound Absorption Spectra of Several Sound Absorption Fibrous Materials3.3 Sound Absorption Spectrum Formula3.4 Discussion on Sound Absorption Spectrum Formula3.5 Maximal Sound Absorption Coefficient： Material Air Permeability and Sound Absorption Coefficient Formula3.6 ConclusionChapter 4 Analysis on Sound Absorption Principle of Thin Fibrous Layer4.1 Introduction4.2 Acoustic Analysis of Thin Fibrous Layer by Application of Membrane Vibration Theory4.3 The Proofs of Fabric Vibration Sound Absorption Theory4.3.1 Determination of the % Open Area of Fabric4.3： 2 Relation Between Fabric Structure Character-istic and Specifi Acoustic Impedance4.3.3 Analysis on Sound Absorption Characteristics Using the Micropore Viscous Sound Absorption Theory4.3.4 Application of the Resonance Theory4.4 ConclusionChapter 5 Vibration Sound Absorption Model of Porous Material5.1 Introduction5.2 Sound Absorption Model and Theoretical Formula of Porous Materials5.3 Discussion and Verification5.3.1 The Relation between the Material Structural Parameters and the Maximal Sound Absorption Coefficient5.3.2 The Formula of Sound Absorption Spectrum5.4 ConclusionChapter 6 Elastic Sound Absorption Principle of Fibrous Material6.1 Introduction6.2 Vibration Sound Absorption Theory6.3 The Comparing and Discussing of the Theory Results and Testing ResultsChapter 7 Resonance Frequency Formula of Densely Porous Material and Sound Absorption Coefficient Formula of Flexible Membrane7.1 Introduction7.2 Resonance Sound Absorption Frequency of Densely Porous Material7.2.1 Micro-perforation Sound Absorption Theory7.2.2 Resonance Sound Absorption Model of Densely Porous Material7.2.3 End Correction of Micro Perforation7.2.4 Comparison and Discussion of Actual Measured Results7.2.5 Situation of Larger and Smaller Perforation7.3 Flexible Membrane Sound Absorption Model and Sound Absorption Coefficient Formula7.3.1 Sound Absorption Model of Flexible Membrane7.3.2 Verification and Discussion of the Sound Absorption Coefficient Formula of Flexible Membrane7.4 Conclusion

章节摘录

　　In chapter 3, the author has discovered that the soundabsorption of fibrous materials is actually in direct proportion tothe relative amplitude of the sound wave and obtainedaccordingly a mathematical relation expression that the soundabsorption coefficient changes with the frequency.　Thetheoretic spectra worked out by this relation expression tallysatisfactorily with the measured spectra of the materials withvarious cavity depth. Further analysis has been made in thischapter concerning this viewpoint, considering that the soundwave actually pushes the material to vibrate.Due to the forcedvibration, the sound energy is absorbed, thus producing ahigher sound absorption coefficient. This viewpoint caninterpret an acoustic phenomenon, that is, when a fabric is usedas a wall facing or a face protective material of a soundabsorber, the sound absorption coefficient is zero or very small,whereas when the fabric hangs independently or there is an airlayer behind, there is a very high sound absorption coefficient.When applying the membrane vibration theory, microporeviscous sound absorption theory and the perforated plateresonance theory to the thin fibrous layer, the author has foundthat the viewpoint that the sound absorption of the fibrous layercomes from the vibration of the material is acceptable. At thesame time, the conclusion arrived at in this chapter that thediameter of the yarn in the fabric is directly proportional to itsspecific acoustic impedance as an example, has proved thisviewpoint.