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Acoustical properties of earplugs

Hiselius, Per LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

En ny mätuppställning har utvecklats och tillämpats på öronproppar (hörselproppar). Mätuppställning gör det möjligt att skatta de akustiska egenskaperna i form av en så kallad tvåport. För objektiva mätningar på hörselskydd använder man normalt sett någon form av artificiellt huvud eller öra, med vars hjälp man mäter insättningsdämpningen. Denna insättningsdämpning beskriver emellertid inte bara hörselskyddets egenskaper, utan även mätuppställningens. Dessutom kräver detta förfarande ett avancerat artificiellt huvud för att på ett korrekt sätt återskapa de akustiska och mekaniska egenskaperna av ett riktigt huvud. Det visas här att man istället kan använda en enkel mätuppställning där man skattar... (More)
Popular Abstract in Swedish

En ny mätuppställning har utvecklats och tillämpats på öronproppar (hörselproppar). Mätuppställning gör det möjligt att skatta de akustiska egenskaperna i form av en så kallad tvåport. För objektiva mätningar på hörselskydd använder man normalt sett någon form av artificiellt huvud eller öra, med vars hjälp man mäter insättningsdämpningen. Denna insättningsdämpning beskriver emellertid inte bara hörselskyddets egenskaper, utan även mätuppställningens. Dessutom kräver detta förfarande ett avancerat artificiellt huvud för att på ett korrekt sätt återskapa de akustiska och mekaniska egenskaperna av ett riktigt huvud. Det visas här att man istället kan använda en enkel mätuppställning där man skattar öronpropparnas akustiska tvåport. För att beräkna insättningsdämpningen kan denna tvåport kopplas numeriskt till en matematisk modell av ett öra. Mätningar har gjorts på sex olika sorters proppar. Beräknad dämpning har jämförts med uppmätt dämpning enligt vedertagen subjektiv metod. Vidare visas att enkla lumpade modeller kan beskriva de akustiska egenskaperna hos tre helt olika typer av proppar, samt att mätuppställningen med gott resultat kan användas för att studera andra akustiska system än öronproppar. (Less)
Abstract
In this study an experimental setup for measurements of high impedance objects in ducts, yielding the acoustical Two-Port properties of the object, is applied to earplugs. A frequently used experimental setup for measuring objective acoustical properties of earplugs is that of artificial ears. Great effort is spent on duplicating the human ear. The acoustical properties of the earplug are thought to be given by the insertion loss. Such a setup, however, gives a ratio of the "response of a system" to that of "another system". The actual properties of the earplug are thereby embedded in a complicated artificial response. A novel approach, presented here, is to use a simple setup. Given the sound pressure level on both sides of the earplug... (More)
In this study an experimental setup for measurements of high impedance objects in ducts, yielding the acoustical Two-Port properties of the object, is applied to earplugs. A frequently used experimental setup for measuring objective acoustical properties of earplugs is that of artificial ears. Great effort is spent on duplicating the human ear. The acoustical properties of the earplug are thought to be given by the insertion loss. Such a setup, however, gives a ratio of the "response of a system" to that of "another system". The actual properties of the earplug are thereby embedded in a complicated artificial response. A novel approach, presented here, is to use a simple setup. Given the sound pressure level on both sides of the earplug for two sufficiently different termination impedances, the Two-Port properties can be assessed. First, a setup is used where the earplugs are fitted in a cylinder. Second, a setup based on molds of the ear canals of a real person is used. For six types of earplugs, the acoustical properties are assessed and numerically coupled to a model of the ear in order to predict the insertion loss. The predicted attenuation is compared to subjective (REAT) attenuation. In addition, experimental Two-Port data is used to model the acoustical behavior of three fundamentally different types of earplugs. It is shown that simple lumped models suffice to describe the acoustical behavior of the earplugs. Furthermore, it is shown that the measurement setup can be advantageously used to assess the acoustical properties of an arbitrary acoustical partition for a wide frequency range. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Associate Professor Poulsen, Torben, Örsted DTU, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Maskinteknik, hydraulik, vakuumteknik, vibrationer, akustik, vibration and acoustic engineering, vacuum technology, hydraulics, Mechanical engineering, acoustic modelling, objective measurement, insertion loss, earplugs, HPE, HPD, hearing protectors, Two-Port, Four-Pole, attenuation, electro acoustics, acoustics
publisher
Engineering Acoustics, LTH, Lund University
defense location
Lecture hall C at "V-huset", LTH, John Ericssons väg 1, Lund.
defense date
2005-01-21 13:15
ISSN
0281-8477
ISBN
91-628-6370-3
language
English
LU publication?
yes
id
6178afa6-274e-4095-a503-30ac4b95258b (old id 544092)
date added to LUP
2007-09-10 09:09:38
date last changed
2016-09-19 08:44:52
@phdthesis{6178afa6-274e-4095-a503-30ac4b95258b,
  abstract     = {In this study an experimental setup for measurements of high impedance objects in ducts, yielding the acoustical Two-Port properties of the object, is applied to earplugs. A frequently used experimental setup for measuring objective acoustical properties of earplugs is that of artificial ears. Great effort is spent on duplicating the human ear. The acoustical properties of the earplug are thought to be given by the insertion loss. Such a setup, however, gives a ratio of the "response of a system" to that of "another system". The actual properties of the earplug are thereby embedded in a complicated artificial response. A novel approach, presented here, is to use a simple setup. Given the sound pressure level on both sides of the earplug for two sufficiently different termination impedances, the Two-Port properties can be assessed. First, a setup is used where the earplugs are fitted in a cylinder. Second, a setup based on molds of the ear canals of a real person is used. For six types of earplugs, the acoustical properties are assessed and numerically coupled to a model of the ear in order to predict the insertion loss. The predicted attenuation is compared to subjective (REAT) attenuation. In addition, experimental Two-Port data is used to model the acoustical behavior of three fundamentally different types of earplugs. It is shown that simple lumped models suffice to describe the acoustical behavior of the earplugs. Furthermore, it is shown that the measurement setup can be advantageously used to assess the acoustical properties of an arbitrary acoustical partition for a wide frequency range.},
  author       = {Hiselius, Per},
  isbn         = {91-628-6370-3},
  issn         = {0281-8477},
  keyword      = {Maskinteknik,hydraulik,vakuumteknik,vibrationer,akustik,vibration and acoustic engineering,vacuum technology,hydraulics,Mechanical engineering,acoustic modelling,objective measurement,insertion loss,earplugs,HPE,HPD,hearing protectors,Two-Port,Four-Pole,attenuation,electro acoustics,acoustics},
  language     = {eng},
  publisher    = {Engineering Acoustics, LTH, Lund University},
  school       = {Lund University},
  title        = {Acoustical properties of earplugs},
  year         = {2005},
}