As we saw earlier in this topic human beings can generally hear ... can hear ultrasound. Ultrasound waves are longitudinal waves just like sound waves, and they cannot pass through a vacuum.

Ultrasound is produced by high frequency vibrations beyond the range of human hearing ... is transmitted by means of longitudinal waves. Ultrasound is used in medicine to break up kidney stones ...

The National Longitudinal Study of Adolescent Health (AddHealth ... Initiated in 1994 under a grant from the National Institute of Child Health and Human Development (NICHD) with co-funding from 17 ...