As a person with incredibly good hearing it irks me to read this. Most people by the time they're in their early thirties can't hear even half the higher frequencies they could in their twenties. This is almost exclusively due to damage to hearing through loud noises, which often affects men more and earlier than women. Although I'm male I started out with great hearing and did my best to protect it. To this day I can clearly hear those devices that people buy that deter rodents and birds. The high pitched whine of electric equipment that many claim doesn't exist is a constant pain.

The Microphone in your phone isn't designed to pick up the frequencies your wife is referring to, in fact most modern smart devices have filters designed to remove any audio beyond the average teams of human hearing. You're "proof" is just you being ignorant of how phones and ears work then assuming your wife is crazy. It's not difficult to get the right audio to test this properly.