Wayne’s World Hearing Threshold Challenge: Pure Tone Hearing Thresholds – fact or farce?

Look at the two audiograms below.  Are they the same or different?   Identify which shows the better hearing.

Staab Chart - Figure 1

View Figure 1 PDF

Actually, the hearing that the audiograms represent is the same, at least relative to the way that hearing is generally tested.

Discussion:

Most pure-tone audiometric hearing threshold testing is conducted using 5-dB increment changes – meaning that any frequency test-retest results could have a 10 dB difference (±5 dB) and still fall within the repeatability range for such measurement increments.

Add to this variation of the actual audiometric threshold differences the variation in hearing aid fitting formulae target 2cc coupler gains (which can vary by as much as 20 dB, Figure 2), and the suggested targets can vary substantially.

Staab - Figure 2View Figure 2 PDF

This combined variability range might be close enough for government work (using a familiar saying that implies marginal performance), but who is fooling who when applying “Quick Fit” programming to hearing aids by those using such measurements?  To add to the quick-fit “folly” is that pure tones measure only the most peripheral of the auditory system (translate this to the most rudimentary, or least significant).  And, why should a professional spend valuable time performing such basic and questionable testing when their time can be better utilized?

It can easily be argued that good hearing aid fitters (excluded are many fitters, regardless of their educational background – i.e., those identified as “hangers” of hearing aids) can often do as good as or a better job of hearing aid fitting by talking with the patient, making informed decisions about what the patient’s amplification needs are, and performing real-ear measurements to actually measure what the hearing aid is doing, without ever looking at a pure-tone threshold.

For those who suggest that applying pure-tone threshold data to a fitting formula at least puts one into the proper ballpark (and that fine adjustments can later be made), begs the question in that they often use a fitting “Wizard” that allows the software to make whatever changes are to be made.  The problem with this is that the dispenser often has no idea as to the what, how, or why of the changes, and often cannot explain this to the patient.  Does this make one a better “fitter,” or a better “hanger” of hearing aids?  It is quite possible that those fitting hearing aids 20 or so years ago might have been better fitters of hearing aids than many today because they had to listen to the patient and make changes to the hearing aid’s performance based on what they knew the changes were intended to produce.  And, to expand upon the opening sentence of this paragraph, and having played semi-pro baseball, just being in the ballpark does not make one a player.

Wayne’s World Challenge:

“Recognizing that pure-tone thresholds will continue to be used to fit hearing aids, I challenge researchers to perform studies to obtain better and more useful pure-tone audiometric thresholds for hearing aid fittings by:

1)      Changing the test protocol

  • Test in 2-dB increments.
  • Allow the patient to self test.  Allow the patient to turn the Hearing Level dial, even looking at the numbers or screen if they choose to (works faster than pushing computer push buttons and compensates for questionable responses).
  • Have patients use a bracketing procedure (psychophysical method of adjustment).
  • Use pulse tones or some other signal that is easily recognized by the patient.

2)      Results expected:

  • Shorter measurement time
  • More reliable thresholds

The patient can do a better job of identifying their thresholds than the tester can who is indulging in considerable guesswork to determine what he/she thinks is the correct response.  Wouldn’t it be better if we had the patient’s threshold rather than the tester’s idea as to what he/she thinks the threshold is?

  • Better ability to approximate fitting formula targets

Thresholds would be more exact (±2 dB), and therefore should provide better agreement with formula target gains, if that is what one wishes to use.

Keep in mind that this challenge is for obtaining pure-tone audiometric thresholds for hearing aid fitting purposes (although I believe that the suggestions would be better for most pure-tone audiometric testing).

Figure 3 shows the audiograms again and the calculated NAL-NL1 2-cc coupler gains for the two different audiograms.   Which target is best for this patient?  One might say both are essentially the same.  If that is the case, then why have hearing aids that can make gain adjustments down to 1-dB, and why have fitting formulae in the first place?  It would seem that if one believes in the concept of selective hearing aid fittings, that the audiogram should be more exact, which would also reflect more accurate target gains, and theoretically, better hearing aid fittings.

Staab - Figure 3View Figure 3 PDF

So, re-read the above, and if you think there might be something to this, then I dare you to perform the suggested measurements.  Actually, I double dare you……….

Wayne’s World