Antonyms of adj supersonic

2 senses of supersonic

Sense 1
supersonic (vs. sonic) (vs. subsonic) -- ((of speed) greater than the speed of sound in a given medium (especially air); "a supersonic bomber flies so fast that it must release its bombs while the target is still over the horizon")

sonic (vs. subsonic) (vs. supersonic), transonic -- ((of speed) having or caused by speed approximately equal to that of sound in air at sea level; "a sonic boom")
subsonic (vs. supersonic) (vs. sonic) -- ((of speed) less than that of sound in a designated medium; "aircraft flying at subsonic speeds")

Sense 2
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 supersonic

2 senses of supersonic

Sense 1
supersonic (vs. sonic) (vs. subsonic) -- ((of speed) greater than the speed of sound in a given medium (especially air); "a supersonic bomber flies so fast that it must release its bombs while the target is still over the horizon")

Sense 2
supersonic, ultrasonic -- (having frequencies above those of audible sound)
       => inaudible (vs. audible), unhearable -- (impossible to hear; imperceptible by the ear; "an inaudible conversation")