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: jbareham@mich.com

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

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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

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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