Couldn't the facebook app just listen for signal fingerprints? For example, Nielsen embeds digital fingerprints into songs so that it can tell what you listen t

Couldn't the facebook app just listen for signal fingerprints? For example, Nielsen embeds digital fingerprints into songs so that it can tell what you listen to without listening to the full audio stream. They simply listen for a certain pattern, and make note when they detect the pattern. You could do the same with with "coffee" or "jogging" or "yoga mat". You don't listen to the conversation audio, you detect audio fingerprints.