Infrasonic, is sometimes referred to as low-frequency sound, this sound is lower in frequency than 20 Hz (hertz) or cycles per second, the "normal" limit of human hearing.
Infrasonic Sound
Infrasonic is applied to sound that refers to sound waves below the frequencies of audible sound, and nominally includes anything under 20 Hz. Some sources of infrasound in nature include avalanches, volcanoes, meteorites, and earthquakes. The eruption of the Fuego volcano located in Guatamala created infrasonic sound in excess of 120 decibels in the range below 10 Hz. Measurements on Mt Erebus, which is an active volcano located in Antarctica, discovered strong ultrasonic sounds while the audible sounds were unremarkable. Sound monitors on the Sakurajima volcano in Japan measured strong signals just before an eruption was created. Ocean waves and storms generate a lot of infrasound. Earlier research of infrasound of hurricanes offer some hope of converting the infrasound signature of an approaching hurricane.
Ultrasonic Sound
Ultrasonic is usually applied to sound which is referred to anything above the frequencies of audible sound, and includes anything over 20,000 Hz.
ultrasonic Sound
Ultrasonic sounds are used extensively for medical purposes and in industries. As I mentioned before, Ultrasounds are high frequency waves (more than 20kHz). Even in the presence of obstacles, they are able to travel along well defined paths. For example, Ultrasound can be used to clean parts located in hard to reach places. Ultrasonic waves are sent into the cleaning solution where the objects to be cleaned are placed. The particles of dirt, grease and dust get detached and drop out due to the high amount of frequency. This helps to clean the objects thoroughly.