Do any general-purpose techniques exist to distinguish live spoken speech from played-back speech samples? For example, if I were to deploy a speaker verification system to authenticate users by voice, I would not want the system to be able to be spoofed by playback of voice recordings.
I think I can imagine at least one technique which might work for certain known combinations of microphones / speakers: If a microphone of sufficient quality captures a novel signal outside the speech band that corresponds (in time) to a signal within the speech band, this would seem to indicate a high likelihood of the sample not being a live speaker (because live speakers don't emit signals outside the speech band). Is this reasoning sound? (No pun intended).