HIS - 140 - Lesson 2 - Test Box Analysis and ANSI PowerPoint
TEST BOX ANALYSIS & ANSI In the United States, the manufacture and dispensing of hearing instruments is regulated by the Food and Drug Administration.
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.
TEST BOX ANALYSIS & ANSI Hearing instruments must pass certain performance parameters. These parameters are defined by the American National Standards Institute (ANSI).
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.
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.
TEST BOX ANALYSIS & ANSI Hearing Instrument Specialist perform a test box analysis which meets ANSI standards—not a manikin or ear simulator.
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.
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.
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.
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.
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.
TEST BOX ANALYSIS & ANSI Other test box measures include: Gain by frequency response Output saturation sound pressure level (OSPL) Harmonic distortion
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.
TEST BOX ANALYSIS & ANSI Gain of a hearing instrument is important in providing enough amplification to create audibility of sound to the patient/client.
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.
TEST BOX ANALYSIS & ANSIThe hearing instrument output informationis important for patient comfort with theelectroacoustic performance of the hearinginstrument.
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.
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.
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.
TEST BOX ANALYSIS & ANSI Compression measurements are also made during test box analysis. We will cover much more regarding compression next semester.
TEST BOX ANALYSIS & ANSI NOTE: A nice description of methodology for ANSI test box analysis is found on pages 186 through 191 in Vonlanthen.