Your aunt and I have tried every remedy we can think of, but, uh, it appears that Chad and Jeremy may well have been stilled forever.

11 seconds sound clip from Batman (1966) - The Bat's Kow Tow (S2E30) TV Series.

You can hear this line at 00:15:21 in the Blu-ray version of the movie.

Quote context

[...]

- There's just not enough time, unless... Unless the effects of the voice-eraser wear off after a while.

- If that's true, we don't have to worry at all.

- Gosh, I hope so.

- You go topside and see if Chad and Jeremy have recovered their voices. I'll push on here.

- Aye, aye, sir.

- Any luck, Alfred?

- I'm afraid not, Master Dick.

- Your aunt and I have tried every remedy we can think of, but, uh, it appears that Chad and Jeremy may well have been stilled forever.

- It may not be long before we're all in the same condition. There must be some way out.

- What is it, Alfred?

- It seems that they want to go out to get their hair done.

- Boy, I thought I'd heard everything.

[...]