Haptic feedback

An apparatus for providing haptic feedback to a user, the apparatus comprising:

• a first piezoelectric transducer array comprising multiple first piezoelectric transducers, respective ones of said multiple first piezoelectric transducers being configured to generate a second signal at a second frequency, and at least one of said multiple first piezoelectric transducers being configured to generate a first signal at a first frequency;
• and
• a second piezoelectric transducer array comprising multiple second piezoelectric transducers, respective ones of said multiple second piezoelectric transducers configured to receive the second signal, and at least one of said multiple second piezoelectric transducers configured to:
• generate a third signal to initiate generation of the first signal at the said at least one first piezoelectric transducer of the first piezoelectric transducer array, the first frequency suitable for providing a haptic feedback signal for a user.

A method comprising:

• emitting ultrasonic signals;
• receiving ultrasonic signals;
• comparing waveforms of the received and emitted signals;
• determining respective times of arrival of the emitting signals;
• and determining emitting locations.