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Document Cover Sheet
Project Number SP-3-4352-RV2
Document Title Acoustic Impedance of Type 3.3 Ear Simulator
Source John R. Bareham
Name: Consultant in Electroacoustics
Phone: 734-665-4224
Fax:
Contact
Complete Address:
309 Riverview Drive
Ann Arbor, MI 48104 Email: [email protected]
Distribution TR-41.3.3
For Incorporation Into TIA Publication X For Information
Intended Purpose of Document (Select one) Other (describe) -
The document to which this cover statement is attached is submitted to a Formulating Group or sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of which provisions are hereby incorporated by reference.
Abstract
The acoustic impedance of Type 3.3 ear simulator, with Shore-OO 35 pinna, is compared to the acoustic impedance of human ears and Type 3.4. This is a very brief summary of data previously published by Bruel & Kjaer. The acoustic impedance of Type 3.3 is shown to be similar to the central distribution of humans. With similar leakage, the acoustic impedance of Type 3.4 is not so similar above 2kHz. Among other differences, the Type 3.4 concha volume is different from Type 3.3, as well as most historic couplers.
TR41.3.3-05-11-004a-Acoustic Impedance of Ear Simulators
This contribution consists of a brief PowerPoint summary of the following complete documents:
TR41.3.3-05-11-004b-Acoustic Impedance Measurements B&K 2005.pdfTR41.3.3-05-11-004c-Acoustic Impedance Measurements B&K 2001.pdfTR41.3.3-05-11-004d-Equivalent Volumes of Ear Simulators B&K 2001.pdf
Why does the acoustic impedance of an ear simulator matter?
“The fundamental purpose of an ear simulatoris to test a receiver
under conditions that most closely approximate actual use by real persons.”
IEEE 269-2002
Please see next slide for illustration . . .
pS
ZS
Receiver
ZEpE
Ear Simulator
Simplified Equivalent Circuit of Receiver & Ear Simulator
High impedance source: ZS >> ZE and q constant, so pE ZE
qpS = source pressurepE = pressure at earq = acoustic “current”ZS = source impedanceZE = ear impedance
Low impedance source: ZS << ZE, so pE constant
pe
q
pe
q
IEEE/STIT: B&K 2001
Volumes of Historical Couplers
Except as noted, equivalent volume of most couplers is about 6cc
Volume of Type 3.4 is larger mostly due to a larger concha.
The Impedance Probe in Use
IEEE/STIT: B&K 2001
Acoustic Impedance of 5 Human Ears at “Normal” force,with Parametric Average
180
190
200
210
220
230
240
100 1000 10000frequency [Hz]
Za*
w [
N/m
5]
Amplitude average
h2002
h2005
h2009
h2010
h2013
M1
M2
M3
M4
HumanParametric
Average
IEEE/STIT: B&K 2001
Note variation in real ears !!
Notice M2 – average about 210dB at about 2.4kHz
Acoustic Impedance of Type 3.3 vs Human Average
180
190
200
210
220
230
240
100 1000 10000frequency [Hz]
Za*
w [
N/m
5]
Amplitude average
BK013
BK010
BK008
BK006
BK004
BK002
M1
M2
M3
M4
Human
IEEE/STIT: B&K 2001M2 of Type 3.3 is about 212dB at 2.6kHz
Acoustic Impedance of Type 3.4 vs Human Average
180
190
200
210
220
230
240
100 1000 10000
frequency [Hz]
Za*
w [
N/m
5]
Amplitude average
HA10
HA08
HA07
HA06
HA05
HA04
HA02.5
HA02
HA01
M1
M2
M3
M4
Human
IEEE/STIT: B&K 2001M2 of Type 3.4 is about 206dB at 2.6kHz
Research & Graph: B&K 2005
Acoustic Impedance Measurements 2005 - New Procedures
Acoustic Impedance of 10 Human Listeners - 2005Impedance measured with probe in form of cell phone. Subjects held probe in natural position, without further instruction, as they would normally hold a phone. Positions were generally different from HATS.
Although the probe was held in positions different from HATS,1. The “natural position” curves are well-grouped, considering human variation2. Type 3.3 “35”pinna in HATS position at 10N simulates the group average well
Research & Graph: B&K 2005
180
190
200
210
220
230
240
100 1000 10000
frequency [Hz]
Za
*w [
N/m
5]
AE 1.6N
APS 2.7N
AS 1.7N
BL 3.7N
ESO 3.8N
ISO 1.5N
JS 3.3N
LBN 3.1N
MK 2.7N
OMI 5.9N
35 10N ERP+2.0mm
55 18N ERP+2.5mm
Note variation in real ears !!
Notice M2 of Type 3.3 – about 210dB at about 2.5kHz
M2
Conclusions:
•Human-like leakage is simulated by Type 3.3 or 3.4
•Leakage is force and/or position dependent
•Both types generally require more handset force than humans use for equivalent leakage
•Acoustic impedance of M1 is similar
•Acoustic impedance of M2 is different
•Type 3.3 M2 is similar to humans
•Type 3.4 M2 is lower, generally resulting in underestimate of receiver response around 2.5kHz (most receivers)
Comparison of Type 3.3, with Shore 35 Pinna, and Type 3.4