AI-FOX: Outcome and targets

AI-FOX establishes the current state of the aided cochlea by means of psychoacoustic tests.  Many such tests exist or can be conceived.

Currently, Audiometry, Spectral Discrimination, Loudness Scaling and Speech Audiometry are performed and all have preset targets.

  • Audiometry is a standard clinical test. It assesses the aided detection level of the cochlea at different frequencies.  For this purpose, 250, 500, 1000, 2000, 4000 and 6000 Hz are chosen because these frequencies span the bandwidth of Nucleus processors
  • The phoneme discrimination test assesses the spectral discrimination capacity of the aided cochlea. Twenty phoneme contrasts are presented in an odd ball paradigm.  The listener is asked to react to the odd phoneme.  The cue for discrimination is a difference in spectral content between the two phonemes.  Coding spectral differences is the core function of the cochlea.  Hence, if certain contrasts cannot be discriminated, this reflects a failure of the cochlea to convey the spectral cue
  • Loudness scaling test presents narrow band noises with centre frequencies of 250, 1000 and 4000 Hz at different levels between 30 and 80-85 dBHL. The listener is asked to score the subjective loudness on a categorical scale ranging from inaudible to too loud.  The scores are compared to those of normal hearing controls
  • Speech audiometry is a standard clinical test in which words are presented at 40, 55, 70 and 85 dBSPL. If possible, monosyllables are used. The listener is asked to repeat the words and the correct phonemes are scored

These four tests have been chosen because they cover the coding of sound at the level of detection (audiometry), discrimination (phoneme discrimination) and identification (loudness scaling and speech audiometry).

Whereas detection and discrimination are core functions of the receptor (the cochlea), identification is not.  Identification requires more than a good receptor alone, it also needs good central processing, cognition, etc. Therefore, the first two tests are more accurate in reflecting the state of the cochlea.

The intensity and spectral components of sound are well covered by the tests chosen.  The coding of TFS (temporal finestructure) is not really tested.  Although this can be done, it is not informative for the current cochlear implants because they all fail to convey TFS information well.

Targets

AI-FOX has targets for each outcome.  These targets are the values obtained in hearing peers; or, if difficult to achieve this, values as close as possible to these normal values.

For a given CI recipient, AI-FOX may individualize the targets, or modify them during the course of the fitting-process, for instance, if several attempts have failed to bring the measured results to the original targets.

Continue reading on AI-FOX’s built-in knowledge…

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