Hearing Profiles

Hearing profiles, or audiograms, vary from person to person. The audiogram specifies the minimum amplitude of sound an invididual is able to hear. For example, in Figure 1, the blue line delineates what the minimum amplitude of the sound at the specified frequency the individual is able to hear. In this case, the individual's needs a sound at 4000 Hz to be a minimum of 60 dB to be hear, which is very poor. The ideal range for minimum dB level is above 20 dB across all frequencies.

The goal of our hearing aid is to be tunable to accomodate these various audiograms. The following is an example of a common type of audiogram for a hearing impaired person. 

Figure 2: Sensorineural Hearing Loss

In Figure 1, you will see an example of sensorineural hearing loss, which is the most common type of hearing loss. 90% of hearing impaired people have this type of hearing loss in which there is damage to the inner ear. 

Figure 2: Conductive Hearing Loss

Figure 2 is an example of conductive hearing loss in which the outer or middle ear are not properly working. This causes a block. 

Figure 3: Mixed Hearing Loss

Figure 3 is an example of mixed hearing loss. Expectedly, this is a mix of both conductive and sensorineural hearing loss. 

Our ideal tunable hearing aid system would attempt to amplify the frequencies for which the individual requires a larger minimum amplitude. In particular, a set of selectively tuned band pass filters would amplify the frequency ranges in which the individual has poor hearing. This set of band pass filters will be tuned by modifying programmable resistor values within each bandpass filter circuit. In particular, the band pass filters can be modified for a different corner frequency, quality factor (or width), and amplitude. 

Based on the above, we may want to focus more on improving the hearing aid performance for sensorineural hearing profiles, since the vast majority of hearing impaired people suffer from this type of hearing loss. Sensorineural hearing may require also having the ability to increase decrease the attenuation of the filter and having a large amplitude, which may require using higher order band pass filters.