Just think, Scooby, no ghostly voice will get past your keen sense of hearing.
5 seconds sound clip from Scooby-Doo, Where Are You! - What the Hex Going On (S1E6).
You can hear this line at 00:04:50.176 in the Blu-ray version of the episode.
Quote context
[...]
- That's strange. The phone's dead.
- Why don't you go get the sheriff, Mr. Wetherby? We'll wait here.
- We'll keep an eye on Uncle Stuart until you get back.
- Are you sure you'll be all right?
- Sure, and just to make sure nothing else happens, we'll all take turn standing guard.
- Who's going to stand the first watch?
- Right. The watchdog. Huh? That's me!
- Just think, Scooby, no ghostly voice will get past your keen sense of hearing.
- Eh?
- Eh? That old hard-of-hearing trick isn't going to work tonight, Scooby.
- Hey, what's with the bugle call, Scooby?
- Uh-oh. It looks like Uncle Stuart's gone again.
- He's not the only one. Sharon's gone, too.
[...]