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HIS - 140 - Lesson 2 - Test Box Analysis and ANSI PowerPoint
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HIS - 140 - Lesson 2 - Test Box Analysis and ANSI PowerPoint

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  • 1. TEST BOX ANALYSIS & ANSI In the United States, the manufacture and dispensing of hearing instruments is regulated by the Food and Drug Administration.
  • 2. TEST BOX ANALYSIS & ANSI The are no ANSI standards for directional microphones—only for proper placement orientation of a directional microphone hearing instrument during the analysis. The is no ANSI standard for battery current drain. However, it is required that the battery drain be measured at the reference test gain.
  • 3. TEST BOX ANALYSIS & ANSI Hearing instruments must pass certain performance parameters. These parameters are defined by the American National Standards Institute (ANSI).
  • 4. TEST BOX ANALYSIS & ANSI The International Electroacoustical Commission (IEC) is also used to establish hearing instrument parameters not defined by ANSI (or required) by the FDA.
  • 5. TEST BOX ANALYSIS & ANSI The key difference between ANSI and IEC is that all electroacoustic measurements are measured in a 2cc coupler while IEC measurements are performed in an ear simulator.
  • 6. TEST BOX ANALYSIS & ANSI Hearing Instrument Specialist perform a test box analysis which meets ANSI standards—not a manikin or ear simulator.
  • 7. TEST BOX ANALYSIS & ANSI Two primary couplers are used in the test box analysis of the majority of hearing instruments dispensed in the United States. They are:1. The HA-1 used primarily for Custom shell hearing instruments2. The HA-2 used primarily for BTE style hearing instruments.
  • 8. TEST BOX ANALYSIS & ANSI Test boxes require two microphones to measure hearing instrument performance.1. A control microphone—to monitor the inside box environment.2. A reference microphone--to be placed next to the hearing instrument microphone.
  • 9. TEST BOX ANALYSIS & ANSI Many test boxes now use a swept broadband stimulus signal. The frequencies presented are received by the hearing instrument and the reference microphone of the test box.
  • 10. TEST BOX ANALYSIS & ANSI A Fourier Transform analysis is then made by the test box to determine the specific frequencies coming through the hearing instrument.
  • 11. TEST BOX ANALYSIS & ANSI High frequency average gain (HFA) and the frequency range are two important factors when selecting hearing instruments for patient/client benefit. See page 81 of Dillon to summarize these calculations.
  • 12. TEST BOX ANALYSIS & ANSI Other test box measures include: Gain by frequency response Output saturation sound pressure level (OSPL) Harmonic distortion
  • 13. TEST BOX ANALYSIS & ANSI Gain by frequency response is measured with a 60dbSPL input level. This represents the amount of gain/volume a hearing instrument posses with a 60dbSPL level input into it.
  • 14. TEST BOX ANALYSIS & ANSI Gain of a hearing instrument is important in providing enough amplification to create audibility of sound to the patient/client.
  • 15. TEST BOX ANALYSIS & ANSI Output Saturation Response Level (OSPL) Measures the maximum sound pressure level generated by the hearing instrument. It is performed with a 90dbSPL input into the hearing instrument.
  • 16. TEST BOX ANALYSIS & ANSIThe hearing instrument output informationis important for patient comfort with theelectroacoustic performance of the hearinginstrument.
  • 17. TEST BOX ANALYSIS & ANSI Equivalent input noise is a measurement taken of any noise generated by the hearing instrument itself. The test box only listens it does not present a signal.Note: This requires that the testing area be in avery quiet environment.
  • 18. TEST BOX ANALYSIS & ANSI Harmonic distortion is the measurement of artifacts in the “clear” electroacoustic performance of a hearing instrument. All amplifiers have measureable distortion. However, they must be within the FDA guidelines for hearing instrument manufacture.
  • 19. TEST BOX ANALYSIS & ANSI Harmonic distortion is measured at the reference test gain setting of the hearing instrument. It is then presented with a 70dbSPL pure tone signal to measure the harmonic distortion of the hearing instrument.
  • 20. TEST BOX ANALYSIS & ANSI Compression measurements are also made during test box analysis. We will cover much more regarding compression next semester.
  • 21. TEST BOX ANALYSIS & ANSI NOTE: A nice description of methodology for ANSI test box analysis is found on pages 186 through 191 in Vonlanthen.