iCHENFIT

Turn your iPhone into an auto-fitting hearing aid.

1. Background

Based on the new loudness models for normal and impaired hearing developed by the author, a new fitting formula named CHENFIT for cochlear hearing loss is achieved recently.

CHENFIT is trying to compensate for outer hair cell loss and inner hair cell loss respectively, according to the different properties of these two kinds of hair cells in human auditory system. Benefit from the new models and new compensation criteria, CHENFIT can do a fast fitting based on audiogram. After fitting, CHENFIT is implemented by accurately mimicking the compressive properties in normal and impaired ears, not like most current fitting formulae which are implemented approximately by multi-channel compression algorithm.

CHENFIT has been applied as Chinese Patent and World (PCT) Patent. iCHENFIT is the version of CHENFIT working on iPhone.

2. User Guide

(1) AUDIOGRAM
Type in the audiogram provided by professional audiologist, then press the “Save and Fitting” button to save the data and do the auto-fitting.

Note: As amplification may cause feedback whistle, this app may be not suitable for hearing loss larger than 60 dB HL.

(2) AMPLIFICATION MODE
“Nonlinear” mode is recommended to be used for cochlear hearing loss (which has damaged outer hair cell and/or inner hair cell, like presbycusis and drug-induced hearing loss). It automatically adjusts the gain for different input levels (more gain for soft sounds and less gain for loud sounds).You are recommended to set the volume button to maximum value for this mode.

CHENFIT now can only find the optimal amplification for average cases (there is still no way to quickly fit each type of hearing loss with optimal gains). Some individual may be bias from average and find that this mode is not so suitable. At the same time, as the user’s device has not yet been calibrated for sound pressure level, some bias may be introduced. In these cases, you can use “Linear” mode instead.

“Linear” mode can be used for users with conductive hearing loss (like having problem in eardrum or middle ear bones) and those with cochlear hearing loss who are not satisfied with “Nonlinear” mode. This mode has a fixed gain for all input levels. So you may need to turn up volume button for soft sounds and turn down for loud sounds manually. Before choosing this mode, please turn down volume button to avoid over-amplification.

(3) TURN ON/OFF
Before turn on, make sure that headset or headphone has been plugged in. When a headset is used, the sound is recorded by the headset microphone; when a headphone is used, the sound is recorded by the built-in microphone in iPhone. Please note that if headset microphone is close to mouth, it will make self-speaking relatively loud. You can use headphone instead if the headset is uncomfortable.

When switch is on, you can lock the screen to reduce power consumption or press home button to do other non-audio tasks; if a phone call is arrived or a Clock/Calendar alarm is invoked, the switch will turn off. After dealing with these interruptions, you can turn on the switch to keep on amplification.

3. Addition Information

This app can be also used by normal hearing people for the purpose of sound amplification(please use "Linear" Mode).

This app has been validated on IOS 5.1 and later. Earlier IOS versions have not yet been tested.