An apparatus comprises a signal source, a driver and an electro-mechanical
transducer. The signal source is configured to output a haptic feedback
signal. The driver is configured to receive the haptic feedback signal
and output a drive signal. The electro-mechanical transducer is
configured to receive the drive signal. The electro-mechanical transducer
is configured to have a set of operational modes. Each operational mode
from the set of operational modes has at least one resonant mode from a
set of resonant modes.