  Acoustic waves at microwave frequencies have been widely used in wireless
communication and recently emerged as versatile information carriers in quantum
applications. However, most acoustic devices are passive components, and
dynamic control of acoustic waves in a low-loss and scalable manner remains an
outstanding challenge, which hinders the development of phononic integrated
circuits. Here we demonstrate electrical control of traveling acoustic waves on
an integrated lithium niobate platform at both room and millikelvin
temperatures. We modulate the phase and amplitude of the acoustic waves and
demonstrate an acoustic frequency shifter by serrodyne phase modulation.
Furthermore, we show reconfigurable nonreciprocal modulation by tailoring the
phase matching between acoustic and quasi-traveling electric fields. Our
scalable electro-acoustic platform comprises the fundamental elements for
arbitrary acoustic signal processing and manipulation of phononic quantum
information.
