Antonyms of adj ultrasonic

1 sense of ultrasonic

Sense 1
supersonic, ultrasonic -- (having frequencies above those of audible sound)

INDIRECT (VIA inaudible) -> audible, hearable -- (heard or perceptible by the ear; "he spoke in an audible whisper")

Similarity of adj ultrasonic

1 sense of ultrasonic

Sense 1
supersonic, ultrasonic -- (having frequencies above those of audible sound)
       => inaudible (vs. audible), unhearable -- (impossible to hear; imperceptible by the ear; "an inaudible conversation")