Pure Tone Group (PTG) Definitions

How were these hearing loss categories created?

The data used to establish these profiles came from over 1200 cases of unaided persons tested at health fairs where threshold and profile information was collected. The use and satisfaction profile information is based on 450 hearing aid users fit with instruments just prior to the 1990's. It is our intention to add more use and satisfaction data with current hearing aid technology as well as incorporate word recognition considerations, as more data are gathered in our own and other cooperating clinics.

In evaluating the person's communication difficulties and satisfaction with hearing aid use we have reasoned that the better ear thresholds (performance) will most closely approximate the person's overall skill in everyday situations.

Self report data were available on approximately 3000 subjects. These were passed through a pass/fail screening filter to separate out failures. The subjects failed the screening if any threshold exceeded 25 dB at 1 or 2k Hz or 30 dB at 4k Hz. There were 1243 who failed this screening.

Using two points on the audiogram (1k Hz and 2/4k Hz average) we generated eight exclusive categories of hearing loss from among the health fair screens who failed. The sorting criteria were as follows:

Flat configurations:

An "F-1" includes thresholds at 1k that are 30-45 dB and 2-4k average less than or equal to 55 dB.
An "F-2" includes thresholds at 1k that are greater than or equal to 50 dB.

Sloping configurations:

An "S-1" includes thresholds at 1k that are 20-25 dB and 2-4k greater than 35 dB and less than or equal to 55 dB.
An "S-2" includes thresholds at 1k that are 40-45 and 2-4k average greater than 55 dB.

Precipitous configurations:

A "P-1" includes thresholds at 1k that are less than or equal to 15 dB and 2-4k average that is greater than 30 and less than or equal to 55 dB.
A "P-2" includes thresholds at 1k that are less than or equal to 35 dB and 2-4k average that is greater than 55 dB.

Minimal loss configurations:

A "4k-1" includes thresholds at 1k that are less than or equal 15 dB and a 2-4k average that is less than or equal 30 dB.
A "4k-2" includes thresholds at 1k that are greater than or equal to 20 dB and less than or equal to 25 dB and 2-4k average that is less than or equal to 35 dB.

Using these criteria we found two flat, two sloping, and two precipitous patterns of common hearing loss, plus two other patterns that showed almost normal hearing except at 4000 Hz. We surmise that these eight different patterns of loss are sufficient to classify nearly all common hearing losses in the population. Future research may show further division based on speech in noise scores.

Pure Tone Groups

We designed the sort criteria so we obtained mean threshold data which were relatively flat for two groups. Here the more severe losses were about 1/6th as common as the milder losses. Two sloping groups were derived with the severe group being 1/4 as common as the milder losses. Two precipitous groups were derived with the most severe losses being about 1/5th as common as the milder losses.
The mean data on two other groups (4k-1, 4k-2) showed loss only at 4000 Hz. These losses were common in our health fair sample but hardly any of these losses were in the hearing aid database.

Health Fair Data

Threshold averages for health fair clients who completed self-assessment forms compared with threshold averages for hearing aid users. The same sort criteria were used in both cases and the averages are similar except in the Flat groups, where the users seem to represent slightly greater losses within these groups.