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TR41.3.3-05-11-004a-Acoustic Impedance of Ear Simulators

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.pdf TR41.3.3-05-11-004c-Acoustic Impedance Measurements B&K 2001.pdf

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TR41.3.3-05-11-004a-Acoustic Impedance of Ear Simulators

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  1. TR41.3.3-05-11-004a-Acoustic Impedance of Ear Simulators

  2. 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.pdf TR41.3.3-05-11-004c-Acoustic Impedance Measurements B&K 2001.pdf TR41.3.3-05-11-004d-Equivalent Volumes of Ear Simulators B&K 2001.pdf

  3. Why does the acoustic impedance of an ear simulator matter? “The fundamental purpose of an ear simulator is to test a receiver under conditions that most closely approximate actual use by real persons.” Please see next slide for illustration . . . IEEE 269-2002

  4. Simplified Equivalent Circuit of Receiver & Ear Simulator Ear Simulator pE ZE q pe q pe Receiver q pS = source pressure pE = pressure at ear q = acoustic “current” ZS = source impedance ZE = ear impedance ZS pS High impedance source: ZS >> ZE and q  constant, so pE ZE Low impedance source: ZS << ZE, so pE constant

  5. 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. IEEE/STIT: B&K 2001

  6. The Impedance Probe in Use IEEE/STIT: B&K 2001

  7. Acoustic Impedance of 5 Human Ears at “Normal” force, with Parametric Average Human Parametric Average Note variation in real ears !! Notice M2 – average about 210dB at about 2.4kHz IEEE/STIT: B&K 2001

  8. Acoustic Impedance of Type 3.3 vs Human Average Human M2 of Type 3.3 is about 212dB at 2.6kHz IEEE/STIT: B&K 2001

  9. Acoustic Impedance of Type 3.4 vs Human Average Human M2 of Type 3.4 is about 206dB at 2.6kHz IEEE/STIT: B&K 2001

  10. Acoustic Impedance Measurements 2005 - New Procedures Research & Graph: B&K 2005

  11. Acoustic Impedance of 10 Human Listeners - 2005 Note variation in real ears !! M2 Impedance 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, • The “natural position” curves are well-grouped, considering human variation • Type 3.3 “35”pinna in HATS position at 10N simulates the group average well Notice M2 of Type 3.3 – about 210dB at about 2.5kHz Research & Graph: B&K 2005

  12. Comparison of Type 3.3, with Shore 35 Pinna, and Type 3.4 • 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)

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