  More and more home appliances are now connected to the Internet, thus
enabling various smart home applications. However, a critical problem that may
impede the further development of smart home is overlooked: Small appliances
account for the majority of home appliances, but they receive little attention
and most of them are cut off from the Internet. To fill this gap, we propose
MotorBeat, an acoustic communication approach that connects small appliances to
a smart speaker. Our key idea is to exploit direct current (DC) motors, which
are common components of small appliances, to transmit acoustic messages. We
design a novel scheme named Variable Pulse Width Modulation (V-PWM) to drive DC
motors. MotorBeat achieves the following 3C goals: (1) Comfortable to hear, (2)
Compatible with multiple motor modes, and (3) Concurrent transmission. We
implement MotorBeat with commercial devices and evaluate its performance on
three small appliances and ten DC motors. The results show that the
communication range can be up to 10 m
