The Acoustic Change Complex in normal hearing adults and adults with sensorineural hearing loss

Our ability to understand spoken language, which is a complex sound consisting
of various frequency and amplitude changes, is related to the ability to
perceive subtle changes in frequencies and intensities of simple sounds as
tones. Patients with sensorineural hearing loss (SNHL) experience frequently
difficulties when they are asked to report small frequency and intensity
changes. An electrophysiology measurement, such as the acoustic change complex
(ACC), recorded from the auditory cortex, might be an appropriate objective
tool, to test whether tone changes are perceived. To date, little is known
about the relation of the perception of small tone changes by normal hearing
subjects and subjects with SNHL and the presence of the ACC.
In this study we aim to assess the level of agreement between the ACC and small
frequency changes, the so called *just noticeable differences (JND)*, perceived
by normal hearing and hearing impaired adults with sensorineural hearing loss.
Subjects will not have a direct benefit of this study, but the results of this
study will contribute to the scientific knowledge of how frequency changes in
stimuli are perceived in the auditory cortex. Furthermore, a high level of
agreement between the ACC and the JND might lead to the development of a new
objective test to evaluate the frequency discrimination in patients who are
unable to reliably report these subtle differences, such as children. The ACC
might also be useful in the follow-up of cochlear implant patients.
Musical training improves frequency JNDs and speech in noise perception.
Because of the therapeutic potential of musical training we like to examine, as
secondary objective, the effect of musical training on ACCs and frequency JNDs.

Primary objective:
To assess the level of agreement between the following tests:
- The minimal frequency difference necessary to evoke an ACC in normal hearing
adults and adults with SNHL (ACC threshold).
- The just noticeable frequency differences perceived by normal hearing adults
and adults with SNHL (JND threshold).

Secondary objectives:
To assess the relation between the speech reception in noise threshold and the
ACC and JND thresholds.
To assess the effect of hearing loss and musical training on ACCs and JNDs
To evaluate the repeatability of the ACC recordings in normal hearing adults
and adults with SNHL within one test session.

24 normal hearing subjects and 24 subjects with sensorineural hearing loss will
be included in this observational study. All participants will be subject to
three tests: ACC recordings, JND tests and speech-in-noise test. A standard
audiogram will be measured to assess the hearing (normal or loss). A music
questionnaire will be completed by the subject to assess the musical training.

The ACC recording, the just noticeable difference tests and the speech
reception in noise tests are considered as a non-risk investigation; adverse
events are not expected to occur during the measurements. The expected burden
due to participation for all participants consists of one session of
approximately 3,5 hours.
Subjects will not have a direct benefit of this study, but the results of this
study will contribute to the scientific knowledge of how frequency changes in
stimuli are perceived in the auditory cortex. Furthermore, a high level of
agreement between the ACC and the JND might lead to the development of a new
objective test to evaluate the frequency discrimination in patients who are
unable to reliably report these subtle differences, such as children. A
confirmation of benefit of musical training for ACC and JND might lead to
hearing therapy based on music.