Can someone remind me how to do the sexy whisper?

I was talking to someone online and he said he wanted to whisper something to me but he didn’t have a mic yet. I’ve had this happen several other times on different platforms, but I wanted to know how to do sexy whispers because I remind them I don’t have my headphones on yet and I can’t hear anything. I wanted to know how to do it so if it happens again I can hear what he wants to say.