An ultrasonic whistle was a device that produced sounds above the normal range of Human hearing.
In 27 ABY, Viqi Shesh used an ultrasonic whistle to activate a Yuuzhan Vong device that, on receiving the ultrasonic signal, would dispense a cloud of sleep-inducing spores into the apartment of her targets, the Solo family.
In 27 ABY, Viqi Shesh used an ultrasonic whistle to activate a Yuuzhan Vong device that, on receiving the ultrasonic signal, would dispense a cloud of sleep-inducing spores into the apartment of her targets, the Solo family.