A Question on Ultrasounds (with pics)

E+
Hi. I would like to know from anyone that has experience with ultrasounds if they actually can harm the baby, hearing or otherwise. I told a friend I noticed that my baby always has his hands up in the air or covering his ears when we get ultrasounds. (Because I'm high risk for a number of reasons I have them almost every week or every other week now. I'm 23 weeks Friday.)
I thought it was sooo cute!!!! Cause i see him and feel it at same time.
21+3 weeks here
 She said The soundwaves may bother a babies ears. She said her son always did the same thing and I notice a lot of other ultrasounds posted look the same. 
She said that's where the name "ultrasound" comes from. They use sound waves to see baby. Is that true? have anyone else heard that? I would really appreciate any feedback thank you
22+3 weeks here