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

instruments

2. 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 & ANSI

The hearing instrument output information

is important for patient comfort with the

electroacoustic performance of the hearing

instrument.

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 a

very 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.