- Wow! We almost got hit by that sandbag!
- Yeah! I guess the rope must have broke!
- Broke, nothing. Look. It's been cut with a knife, and ropes don't cut themselves.

12 seconds sound clip from Scooby-Doo, Where Are You! - The Backstage Rag (S1E9).

You can hear this line at 00:11:22.157 in the Blu-ray version of the episode.

Quote context

[...]

- And don't forget, if you see anything suspicious, bark three times.

- Huh? Hey, Scoob, watch what you bump into.

- I didn't do it.

- A guy could get hurt around here. Come on. Let's go look somewhere else.

- Gee, Velma, I wish we had a clue to a clue.

- Don't worry, Daphne. If we stick around here, we're bound to find something.

- Wow! We almost got hit by that sandbag!

- Yeah! I guess the rope must have broke!

- Broke, nothing. Look. It's been cut with a knife, and ropes don't cut themselves.

- Let's look along here in the dressing room area.

- OK, Raggy.

- Hey, there should be a lot of junk in here to check over.

- Let's browse around here a bit, Scooby.

- Right.

- Hmm? Hmm? Should I look?

[...]