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New Controllable Sound Absorbers Made
of Vacuum Packed Particles
ZalewskiRobertandRutkowskiMichał
InstituteofMachinesDesignFundamentals,
84NarbuttaSt.,Warsaw,02-524,Poland
robertzalewski@wp.pl, landranger@gmail.com
Abstract.
Thisarticlerevealsapartofexperimentalresearchperformed
onSpecialGranularStructures(SGS).These structureshavesomefea-
turesthatarecommontosmartmaterials.Authors'earlierpapersfrom
lastdecadewerefocusedmainlyonresearchandmodelingofthemechanics
ofthediscussedmaterials.Possibilitiesofchangingthephysicalproperties
ofgranularmaterialsurgedtheauthorstotryandtestexperimentallyif
theacousticparametersofgranularstructuresmayalsobecontrolledby
theunderpressureparameter.Aseriesoflaboratorytestsregardingthein-
fluenceofselectedparametersonthesoundabsorptioncoecientofSGS
provethatthereisasimplewayofcontrollingmentionedtheacousticchar-
acteristicsoftestedstructures.Thisuniquefeatureenablestheirusageas
apartofmulti-laterabsorbingstructureswithvariablecharacteristics.
Keywords:
specialgranular structures,absorption coecient,control-
lablesoundabsorption.
1
Introduction
The problem of extensive noise is closely related to the operation of machines
and devices on both the industrial and the individual level. Long exposure to
elevatedsoundlevelscancause,apartfromlonglastinghearingdefects,problems
withmainhumanorganismsystems:nervous,breathingorevencirculatory.It
ismentionedmoreandmorefrequentlyindifferenttypesofliteraturethatthe
numberofpeoplewithallsortsofhearingproblemsisstillrising.Someofthe
mainreasonsforthisareprobablythefashiontowardslisteningtomusicthrough
headphones and being exposed to very high volume (beyond any admissible
levels)noiseatmusicevents.Beyondanydoubt,transportationalandindustrial
noisesarealsoguilty.
Apart from obviously harmful factors, there are other problems with inter-
mediatelevelsofnoisethatarebothersomeforhumans.Thesecauseproblems
withconcentrationanddecreaseworkeciency.
Thedescriptionaboveshowsthatproblemswithunwantednoiseismoreand
morenoticeableineverydaylife. Onthe otherhand,it shouldbenoticed that
thereisanincreaseinconsciousnessofthedangersandrisksrelatedtonoisein
currentsocieties.
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