I think the reason they might need placebo may be due to the stated minimum efficacy measurement factor of 10 dbhl improvement. I think it's plausible that placebo could affect (i.e. effectively improve) hearing perception to the minor degree of 5-10 DB, much the same as stress or tiredness might. Remember, they're trying to isolate and detect a minimal degree of improvement at this point.
But just rememebered that hearing improvement is not actually a stated endpoint here. Still posting this as it may be generally relevant.
Placebo could also be relevant in terms of harmful effects: if, say 10% of the trial (real treatment group) report inner ear pain following treatment; but 10% of the placebo group report the same, that would suggest that the side effect of pain is not due to the drug specifically.
But just rememebered that hearing improvement is not actually a stated endpoint here. Still posting this as it may be generally relevant.
Placebo could also be relevant in terms of harmful effects: if, say 10% of the trial (real treatment group) report inner ear pain following treatment; but 10% of the placebo group report the same, that would suggest that the side effect of pain is not due to the drug specifically.