Vibrations below 20 cycles per second (less than 20 Hz) we cannot hear, but we can feel them.
Transonic being past the speed of sound and subsonic is below the speed of sound.
subsonic
If accelerating to the speed of sound, the subsonic.
If the flow is subsonic the pressure will increase, if however it is supersonic the pressure will decrease.
The atmospheric inlet air will convert from subsonic to supersonic condition at the duct area in ram jet engine.
Subsonic signals are sounds or vibrations that have a frequency lower than that which may be heard by the human ear as a discernable tone. Vibrations lower than 30 Hz (30 cycles per second) are considered subsonic.
Low frequency sound is usually called "infrasound" analagous to the term "infrared" for light of less than visible wavelengths. Subsonic has also been used.
The antonym for subsonic is supersonic.
Infrasonic.'Subsonic' and 'infrasonic' both define sound too low (in frequency or pitch) to be heard by humans without assistance.However, as 'subsonic' can also mean something traveling slower than the speed of sound, and 'infrasonic' only means frequencies below the audible range, 'infrasonic' is the better answer.
Subsonic means "slower than the speed of sound" so a subsonic bullet is any bullet that travels slower than the speed of sound.
Subsonic - media server - was created on 2005-02-10.
Supersonic
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subsonic is lower than 20Hz, and hypersonic(aslo called ultrasonic freq.)is higher than 14000Hz-16000Hz(you cant hear ultrasonic freq.,some people hear 50-14000,some 150-16000, even some like me hear 20-16500)my specter of hearing freq.is 32-16347Hz(I have been on tests)
Transonic being past the speed of sound and subsonic is below the speed of sound.
Another term for this is infrasonic, and it means pertaining to below hearing. There natural frequencies that humans can hear which are high: 20,000 Hz and low: 20 Hz. An average human cannot hear sounds below the frequency of 20 Hz. That is subsonic. Subsonic is a term also applied to aircraft that travel at speeds less than the speed of sound. Supersonic means it travels faster than the speed of sound.
subsonic is moving below the speed of sound, supersonic is faster than speed of sound