Why would increasing ocean acidity result in a noisier ocean

H^+ ions move extremely rapidly in water much more so than say the Na^+ ions in sea water. The mechanism that is believed responsible for this rapid movement is called the Grotthuss Mechanism:
http://en.wikipedia.org/wiki/Grotthuss_m…
Presumably the more protons there are in the ocean the more the sound waves get amplified and transmitted.
Other than that it may be the whales crying out for some tums?

Who told you that increasing acidity would make the oceans noisier? If anything, it might kill most of the marine life and perhaps that would make the oceans quieter.