University of Puget Sound Sound Ideas Summer Research Summer 2016 e Acoustics of Harmon Mutes Zachary T. Armstrong [email protected] Follow this and additional works at: hp://soundideas.pugetsound.edu/summer_research Part of the Other Physics Commons is Article is brought to you for free and open access by Sound Ideas. It has been accepted for inclusion in Summer Research by an authorized administrator of Sound Ideas. For more information, please contact [email protected]. Recommended Citation Armstrong, Zachary T., "e Acoustics of Harmon Mutes" (2016). Summer Research. Paper 265. hp://soundideas.pugetsound.edu/summer_research/265
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University of Puget SoundSound Ideas
Summer Research
Summer 2016
The Acoustics of Harmon MutesZachary T. [email protected]
Follow this and additional works at: http://soundideas.pugetsound.edu/summer_research
Part of the Other Physics Commons
This Article is brought to you for free and open access by Sound Ideas. It has been accepted for inclusion in Summer Research by an authorizedadministrator of Sound Ideas. For more information, please contact [email protected].
Recommended CitationArmstrong, Zachary T., "The Acoustics of Harmon Mutes" (2016). Summer Research. Paper 265.http://soundideas.pugetsound.edu/summer_research/265
TheAcous*csofHarmonMutesZachArmstrong,RandWorland
DepartmentofPhysics,UniversityofPugetSound,Tacoma,WA
Introduc)onHarmonmutesareusedbytrumpetplayerstoaCainadifferentsoundthanisnormallyproducedbytheinstrumentbyinser*ngtheHarmonmuteintothebelloftheinstrument.ThesoundisoFendescribedasasoFersoundwithadis*nc*vebuzztoit.MilesDaviswasapopularemployeroftheHarmonmute.Althoughtrumpetsthemselveshavebeenthoroughlystudied,theacous*csoftrumpetmutesremaintobefullyunderstood.Somejazzmusiciansbelievethatden*ngHarmonmutescanleadtoanimprovementinsoundandintona*on.Theacous*csofden*ngHarmonmuteswasinves*gatedusingimpedanceandsoundspectrummeasurementsinthehopesofdeterminingthespecificacous*ceffectsofden*ngmutes.
Figure1.AHarmonmuteinthebellofatrumpetreadyforperformance.
Figure2.TwoHarmonmutes.Onedentedandoneundented.
MethodsAcous*cimpedancemeasurementsgivespecificinforma*onaboutalltheresonancesoftheinstrument.Smallchangestoaninstrumentoramutecanbedetectedwithchangestotheimpedancespectrum.TheBIASsystemisastateoftheartimpedanceheadthatcanbeusedfortakingimpedancemeasurementsofbrassinstruments.TheBIASsystemhastheadvantagethatitdoesnotrequireactualplayingoftheinstrument,soresultsare100%reproduciblewithdifferentusers.Becausethisinves*ga*onisfocusedonhowthesoundofHarmonmuteschanges,soundspectrawerecollectedtohelpquan*fyanychangesthatmightbedetectedwiththeear.Soundspectraweretakenbyplayingintoamicrophoneconnectedtoapreampwhichoutputsthesignaltoaspectrumanalyzer.Soundspectraaredependentontheplayerandonthenotebeingplayedandthusarenotasversa*leasBIASmeasurements.Modifica*onstotheHarmonmuteswereeitherdentsorholesplacedsequen*allywithdatabeingtakenaFereachfurthermodifica*on.Dentsweremadewithahammerandholesweremadewithadrillpress.
Figure3.TheBIASsysteminplaceformeasurementoftheimpedancespectrumofatrumpet.
AcknowledgementsIwouldliketothanktheMcCormickfamilyforprovidingthefundstopursuethisresearch.IwouldalsoliketothankGregEllioCandBobPeasleefortheirhelponthisproject.
Figure4.ImpedancespectrumofatrumpetandHarmonmute(redcurve)overlaidonaspectrumofanormaltrumpet(bluecurve).
Themoststrikingdifferencesbetweenthespectrumofthenormaltrumpetandistheseriesofraisedpeaksabove1400Hzwherethepeaksinthetrumpetspectrumfadeaway.Thislossofhighfrequencyresonancesisassociatedwiththeshapeofthebellofthetrumpet.Itseemsini*allythatthemutereturnsthesewavesbacktotheinstrumentsincethepeakshavealsoreturned.Itwasfoundthatothertrumpetmuteshadasimilareffectofraisingmorehighfrequencypeaks.Apreliminaryden*ngexperimentwasconductedtodeterminethebasicac*onofthesemodifica*onsontheimpedancespectrum.
Figure5.Overlaidimpedancespectrafromtheini*alden*ngexperimentshowingwherethemajorityofthechangeshappened.
Figure6.Overlaidimpedancespectrafromtheini*aldrillingexperimentshowingwherethemajorityofthechangeshappened.
Results
Figure7.ImpedancespectraoftheHarmonmuteaFervariousamountsofden*ngordrillingshowingdifferentchangestothespectrumfordifferenttechniques.
Figure8.Soundspectrafromthethirddrillingexperimentshowingthelossofhighfrequencypeakscausedbythemutepeakapproachingthefundamental.GraphsontheleFarenormalsoundspectraandgraphsontherightaresoundspectrafromwhenthosenotesceasetosoundgood.
Asseenabovethemajorityofthechangestotheimpedancespectrumaretothelowerfrequencypartofthespectrumwiththehigherpeakslargelyunaffected.Thiswasunexpected,astheraisingofthosepeaksareduetothemutebeingused.Apreliminarydrillingexperimentwasconductedtoseeifchangestothehighfrequencypartofthespectrumcouldbeobtained.Smallaperturesareknowntocauseabuzz,whichisnotonlyassociatedwithHarmonmutesbutisalsoassociatedwiththepresenceofhighfrequencyharmonics.
PuZngholesinthemutehadanalmostiden*caleffectontheimpedancespectrum.Therewerechangesinasimilarfrequencyrangeasbefore,withthehighfrequencypeaksbeinglargelyunaffected.
Thechangestotheimpedancespectrainthepreliminaryden*ngexperimentswerelargelyduetotheshiFingofthesmallresonanceassociatedwiththemuteitself.Thissmallpeakisnormallyabsentfromspectraoftrumpetswithanopenbellandwasfoundtomovetoahigherfrequencywhenholesordentswereplacedinthemute.Anothersetofden*nganddrillingexperimentswereconductedwithimpedancedatatakenofthemuteitself,withoutthetrumpet.
Asseenabove,den*nganddrillingaffectdifferentresonancesofthemute.Giventhatthelargemuteresonancesdonotshowupintheimpedancespectrumofthetrumpetandthemute,liCleisknownabouttheireffectontheimpedancespectrum.However,den*nganddrillingwerefoundtohaveasimilareffectonthesoundoftheinstrument.Beyondacertainpoint,thesoundbecameweakanddifficulttoplayintune.Thiswascharacterizedinthesoundspectrabyalossofhighfrequencypeaks.Inanotherdrillingexperimentmanyholeswereplacedinthemute,causingthemutepeaktoshiFupaconsiderableamount.Itwasnotedthatthe*meapar*cularnotebegantosoundweakorbadwasaroundthe*methemuteresonancewasclosetothetrumpetresonancecorrespondingtothatnote.
ConclusionsPlacingdentsandholesinHarmonmuteswerefoundlargelytodegradethesoundoftheinstrument.Thisisbecausechangestotheresonanceofthemuteaffectstheresonancesofthetrumpet.Itwasfoundthatsmallamountsofden*ngcouldchangethetoneinaposi*vewayandevenmakethemutelouder.Perhapsdentedmuteswouldbesuitedforsec*onworkinjazzorchestrasandundentedmutesarebeCerforsolosandsmallformatgroups.Thedis*nc*vesoundoftheHarmonprobablycomesfromtheraisedsetofpeaksaround3000Hzseeninthesoundspectra.Thissoundandthesepeaksgoawaywhenthemuteismodifiedtoomuch.FurtherworkshouldincludeamorecarefulstudyofhowtheotherpeaksintheimpedancespectrumofjusttheHarmonmutecometoinfluencethesoundoftheinstrument.Itwouldalsobeinteres*ngtorepeatthedrillingexperimentswithsmallersizedholestotrackmorepreciselythechangesinthesoundandacous*csofthemuteandinstrument.
Normal
Dented
Drilled
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