- Pardon me?
- Oh, I'm just mumbling.

4 seconds sound clip from the Ocean's 11 (1960) movie soundboard.

You can hear this line at 00:11:19 in the Blu-ray version of the movie.

Quote context

[...]

- Do you remember those rum drinks at the Traders?

- I haven't had rum since.

- Those were the olden, golden days, weren't they?

- Do you know about Tony?

- Yes. It's a shame.

- He's getting out tomorrow morning.

- Tomorrow? I thought they gave him one to five.

- They did, but they gave him an amnesty. I don't know why.

- That Danny, always a step ahead.

- Pardon me?

- Oh, I'm just mumbling.

- Will you have Tony call me when he gets home? Tell him to call me...

- He won't be coming home, Roger. That's all finished.

- I didn't know that.

- Well, won't he see the kid?

- Sure, he'll see Timmy, but he'll see him at the Peninsula Military School in the presence of Major Taylor.

- Can I use your phone, Gracie?

- Sure.

[...]