Symphonic bells of ‘‘fantastic’’ proportion

Symphonic bells of ‘‘fantastic’’ proportion Daryl Caswell Citation: The Journal of the Acoustical Society of America 92, 2379 (1992); doi: 10.1121/1.404799 View online: https://doi.org/10.1121/1.404799 View Table of Contents: https://asa.scitation.org/toc/jas/92/4 Published by the Acoustical Society of America MONDAY AFTERNOON, 2 NOVEMBER 1992 BAYOU II, 1:30 TO 3:45 P.M. Session3pMU Musical Acoustics: Musical Instruments Uwe J. Hansen, Chair Departmentof Physics,Indiana State University,TerreHaute, Indiana 47809 Invited Paper 1:30 3pMU1. Time-domain simulations of stringedandpercussion instruments.AntoineJ. Chaigne (Signal Dept., Telecom Paris, 46 rue Barrault, 75634 Paris Cedex 13, France) The tonesof existinginstrumentsare simulatedin the time domainby meansof standardfinitedifference methods.The stringmodelpreviously appliedto the guitar[A. Chaigne,J. Acoust.Soc.Am. Suppl.1 88, S188 (1990)] and morerecentlyto the piano[A. Chaigne,A. Askenfelt,and E. Jansson, J. Acoust.Soc. Am. 89, 1878(A) (1991)] hasbeenextendedto the violin,the xylophonebars,and tympanimembranes. The generalprocedure, whichis similarfor eachtype of instrument,will be presented. It consists firstin derivinga numericalscheme fromthe continuous differentialequations governing the motionof the vibrating systemsincludingthe interactionwith an exciter(hammer,bow, mallets ....). In a secondstep,the mathematicalpropertiesof thesediscreteapproximations are evaluatedwith specialemphasislaid on stability,accuracy,anddispersion problems.Simulatedwaveformsare computedwith realisticvaluesof the parameters derivedfrom measurements on existinginstruments. Thesewaveformsas well as their spectral contentsare then systematically comparedwith thoseof real tones.This time-domainapproachis usedin orderto testthe influenceof variousphysicalparameterson the transientsof stringsand percussive sounds in which the nonlineareffectsare essential.The paperwill be illustratedby soundsynthesis examplesof variousinstrumentsobtainedwith this technique. Contributed Papers 2:00 3pMU2. Comparisonand predictionof modal parametersof a strung and unstrungpiano soundboard. Duane Leggert,Michael W. Miller, and Robert D. Celmer (College of Eng., Univ. of Hartford, 200 Bloomfield Ave., West Hartford, CT 06117) The first eight modesof an unstrungSteinwaymodel-K upright piano soundboard were measuredby testingboth the front and back sides.Strongsimilaritiesin the first eightmodalfrequencies and mode shapeswerefoundeventhough40% fewertestpointswereusedon the back side.Using the dynamic modificationfeatureof the STARStruck modalanalysissoftwaresystem,a predictionof modalparameterswas performed for thestructuralfeaturesof a strungpiano.Comparison of theseresultsto theactualmodalfrequencies andmodeshapes foundby testingthe back sideof a strungpiano soundboard will be discussed. [Work supported by Steinwayand Sons.] 2:15 3pMU3. Modal analysis techniques applied to sound field representation. Uwe J. Hansen (Indiana StateUniv., Terre Haute, IN 47809) and Ingolf Bork (Physikalisch-Technische Bundesanstalt, 3300 Braunschweig,Germany) In structuraldynamics, modalanalysispermitsnormalmoderepresentationfor vibratingstructures by recordingmultipletransferfunctionsand lettinga computeranimatea simpleharmonicoscillatorapproximationto displaynormalmodemotionin an expanded timeframe. 2379 J. Acoust.Soc.Am.,Vol.92, No.4, Pt. 2, October1992 This work showsan exampleof applyingthis techniqueto the representationof a soundfield.Phaseinformationis recordedby usingthe excitationsourceas a referencesignal,monitoringthe soundfieldwith a microphone,and forminga transferfunctionof the two with a dual channelFFT analyzer.The methodis illustratedby showingthe sound fieldaboveand belowthe soundboardof a grandpiano,and in a vertical plane in the generaldirectionof an audience. 2:30 3pMU4. Symphonicbells of "fantastic" proportion. Daryl Caswell (Dept. of Mech. Eng., Univ. of Calgary, 2500 University Dr. N.W., Calgary, AB T2N 1N4, Canada) Producingthe soundof a largebell in an orchestralsettingis consideredto be oneof the mostsignificantunsolvedproblemsof the percussionist. A real bell of the properfrequencyrangeis too large to controlin performanceand too cumbersome to suspendor transport. The useof bell platesin placeof actualbellshashad limitedsuccess due to the difficultiesencounteredin producingaccuratepitch, sufficient amplitude,and a reasonable frequencyresponse. This paperis basedon a novel,multidisciplinaryapproachthat hasresultedin the production of bell plateswith markedimprovementin the mostproblematicareas. The musicalvalue of the researchhas beendemonstratedby two bell platesdesignedto producethe soundof distantchurchbellsin the final movementof Hector Berlioz's$yrnphonieFantastique.The plateswere usedin performances by both the CalgaryPhilharmonicand the VancouverSymphony. 124thMeeting:Acoustical Societyof America 2379