There are many different types of ultra sonic devices. One that almost everyone is familiar with is the ultra sound. There are studies looking at what excessive use of these devices can cause, but if used in moderation they haven;t found them to be harmful. You can check http://www.ultrasoundtechnicianschools.org/are-ultrasounds-dangerous/ for more information.
No but they do help quite a bit
Assuming you mean a super form called Ultra Sonic, No
Correction, Yes there are such beings as Solar Sonic and Ultra Sonic, however, they does not make an Apperance in any of the games, Solar and Ultra Sonic only appeared in the Comics, Ultra Sonic was the Base form Sonic would Assume when he collected a certain Number of Rings (1000 i believe) and he could change his form based on the climate of the Area he is in, Solar Sonic assumes control when Ultra Sonic is in a hot, Arid area, such as a Desert, there is also Eco Sonic for forests and Polar Sonic for Ice caps
Ultra Sonic first appears in Sonic the Hedgehog #'s 65 and 66, with additional appearances in Sonic the Hedgehog #71 and Super Sonic Special # 15.
they change colors
Sonic the Hedgehog - 1993 Ultra Sonic 1-3 was released on: USA: 2 October 1993
no
ultrasound, ultramodern, ultravioletUltramarine, ultramontane, and several hyphenated words such as ultra-violet, ultra-vires, ultra-sonic and ultra-microscope
Dark sonic Hyper sonic Normal sonic Metal sonic (created by Eggman ) Werehog sonic Fire sonic
ultra sounds are used for seeing a baby in an ultra sound
sound waves with frequencies 20 hertz or lower are infrasonic and waves above 20,000hertz are ultra sonic!
Yep but only seen in the comics. It replaced Hyper Sonic in the comics.