How large a role does NIHL play in corporate budgets?

Institutional savings as a result of addressing NIHL can reach the hundreds of millions.

Answer Extra: 

From 1974 to 1994, the US Army saved $504.3M by reducing hearing loss in combat personnel through a dedicated Hearing Conservation Program. Between 1987 and 1997, the Army and the Department of Veterans Affairs saved another $149M and $220M, respectively, by reducing civilian hearing loss.

source: 
source: NIOSH Pub. No. 2001-103