That's a great question, this might be of interest to you:

https://law.stackexchange.com/questions/5614/if-other-party-...

The top answer states:

>Once AT&T, or anyone else for that matter, states that the communication is being recorded, it is no longer considered a confidential communication requiring the consent of all parties in order for any party to record it.

IANAL either, but I think either of informing the party upfront or soft beeps in the background are acceptable.

I've been informed by the other side many times that the call was recorded, and never once heard soft beeps. I think the announcement must be enough.

EDIT: IANAL

Yes. I believe either is sufficient, not that both are required