[Idiom] sound about?

[zildzicahmed]

I could not find this verb anywhere. I found 'to sound out' but not 'sound about'. Example:

"But certainly he was at great pains to sound foreign diplomats about the possible effects of this treaty on European public opinion..."

It appears to me that the meaning here could be that of 'sound out', e.g. to informally find out where they stand in regard to..., but still not sure.
Any thoughts? Thank you!
Ahmed

 

[5jj]

He is sounding (out) the diplomats about the effects.

'about' is a preposition here; it is not part of any phrasal verb.

 

[zildzicahmed]

Thank you 5jj!