Remote ranging using vibrations and ultrasonic transmission

This disclosure addresses the problem of ranging or imaging a remote environment, e.g., a remote conference room, using audio equipment present at the remote location. Ultrasonic waves are transmitted, e.g., via standard telecommunication channels, from the near end to the remote location, and their reflections off objects at the remote location are received at the near end. The reflections are used to reconstruct the remote environment and form an ultrasonic signature. The techniques of this disclosure can be used to secure a phone call, e.g., to verify the identity of the remote party; verify the remote location; differentiate humans from bots at the remote location; verify the number of individuals present at the remote location; verify the identity of the devices being used at the remote location; etc. In addition to ultrasonic waves, devices are remotely vibrated to characterize the surface on which the device rests