New Features on the FONIX FP35 Hearing Aid Analyzer

Version 6.00

Hardware Features

Battery Current Drain

External Input (v5)

Line In

Software Features

Improved Digital Speech Test for Frequency-Shifting Hearing Aids Modified NAL-NL1 Fitting Rule for low to

moderate gain hearing aids 1/3 Octave Analysis

Improved Digital Speech

Digital Speech signal sometimes interfered with feedback management and other advanced features on some hearing aids

Modifications have been made to improve test results

New feature automatic with DIG SPCH is the selected input source

A little theory… Noise Reduction

Sample from Microphone

Averaging to remove

noise

Frequency Analysis

Old Method

Great for eliminating momentary noise, but a problem when testing new, complex hearing aids with feedback management and other advanced features.

New Noise Reduction with Digital Speech and Spectrum Analysis

Sample from Microphone

Averaging to remove

noise

Frequency Analysis

New Method

Should produce a smoother frequency response without interfering with feedback management software.

Also: Smoothing has been added to Digital Speech measurements in Coupler Multicurve.

Comparison of test results using Digital Speech

Version 5.01 software Version 6.00 software

New Test for Freq-Shift Hearing Aids Graph entire response of hearing aid to a

pure-tone signal (default: 4000 Hz)

Input signal

Peak response

Choose DIG FS with F4 in Coupler Multicurve Screen to perform test

DIG FS showing no frequency shift

Modified NAL-NL1 Targets

Some customers have reported that NAL-NL1 targets are hard to fit with some moderate gain hearing aids

Competing analyzers have version of NAL-NL1 with less gain prescription

We have created a “MOD NAL” target that prescribes 3 dB per octave less gain than standard NAL-NL1

Both NAL-NL1 and MOD NAL are available in v6.00 software

Comparison of NAL-NL1 and MOD NAL

NAL-NL1 standard target MOD NAL reduced target

Note: Audiogram used to create these targets is flat 30 dB HL

Modified formula affects both Real-ear SPL and Real-ear Insertion Gain targets

100 Hz FFT vs Third Octave Analysis

Third Octave analysis

100 Hz FFT analysis

First: Thought Experiment: 100 Hz vs 50 Hz Analysis

Think of the output of a frequency response as energy.

Each point on the response is a “bin.”

More bins = better resolution, less output per bin

100 Hz FFT Analysis vs Third Octave All FONIX analyzers perform

“100 Hz FFT” analysis Frequency response is divided

into 79 different points that are 100 Hz equidistant (200, 300, 400… 7900, 8000 Hz)

In Third Octave analysis, frequency response is divided into 17 different points: 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300, and 8000

Third Octave analysis has been resolution in the low frequencies and less resolution in the high frequencies due to logarithmic scaling

Difference between 100 Hz FFT and Third Octave analysis is 3 dB per octave

Important Notes

This 3 dB per octave difference only occurs when viewing results in terms of dB SPL (coupler or real-ear). Gain measurements are not affected.

This difference only occurs when using broadband signals. During a pure-tone sweep, only one “bin” is filled at a time, so the energy is not distributed.

Third Octave analysis on the FP35 analyzer

Available in Real-ear SPL and Coupler Multicurve test screens.

Visible Speech Updates

Speech signal input

RMS Output

Diamonds = Peak Pulsed Average Decay

Use a connected CD player or iPod for the input signal!