A nerve modulation device includes a first ultrasound transducer and a second ultrasound transducer. The first and second ultrasound transducers are configured to emit a first and second ultrasound waves, respectively, that exhibit different frequencies. The first and second ultrasound transducers can emit the first and second ultrasound waves in directions that are selected to cause the first and second ultrasound waves to intersect with each other at an intersection site that is at or near a selected nerve. At the intersection site, the first and second ultrasound waves can non-linearly interact to form an acoustic wave exhibiting a frequency that is less than the frequencies of the first and second ultrasound waves. The acoustic wave can modulate a selected nerve.