A new study published in the journal Reproductive Biology and Endocrinology suggests that applying ultrasound to testicles could be an easy method of contraception since it temporarily destroys the germ cells that produce the sperms.
Researchers from University of North Carolina tested the technique on rats and found that applying a three megahertz high frequency ultrasound beam around the rats' testicles for a period of 15 minutes reduced the number of sperms to below 10 million sperm per milliliter. In humans, a man is considered to be infertile when his sperm count is below 15 million per milliliter.
The researchers said that the technique produces temporary infertility in men which can be reversed later on. However they admitted that more studies need to take place on the subject in order to ascertain how long the effect lasts and whether it is safe to apply the beam again and again.