The literature available on CIST is small. 4 articles that I could find. 3 in English and one in Spanish. This is the Spanish article. Of note is that they used music for 12 hours a days, and used both speech and music.
Here’s an English abstract:
Here’s the original Spanish article:
Terapia sonora en sordera súbita
Here’s a summary translation of the article by Google.
“The combination of music and words has been used by using the songs that the patient likes most or listening to radio stations, interchangeably. In this way, it is intended that the entire cochlear spectrum and its auditory cortical representation will be stimulated, and can also reach different emotional brain regions (prefrontal, temporal or parietal) through the neural networks to stimulate their recovery.
The practical way of Getting the appropriate intensity for each patient is as follows: they are told to place the earphone in the healthy ear with the music and when they begin to hear it minimally (range of 60 ± 10 dB) to put it in the diseased ear. It may be that at that moment you do not hear it through the ear of sudden deafness, being able to hear it when hearing recovery occurs. Even if cophosis has occurred, the same procedure is followed.
The duration of sound therapy is 12 hours a day for 30 days. This sound therapy was applied to the second group of patients (n = 67) together with the medication.”
Translated by Google from Terapia sonora en sordera súbita
CIST and SSHL 