On the left is a normal testicle. On the right is one that has been blasted with ultrasound. The latter has a reduced sperm count, which is why researchers at the University of North Carolina think that they may have discovered an effective male contraceptive:

They found that two, 15-minute doses "significantly reduced" the number of sperm-producing cells and sperm levels. [...]

Lead researcher Dr James Tsuruta said: "Further studies are required to determine how long the contraceptive effect lasts and if it is safe to use multiple times."

The team needs to ensure that the ultrasound produces a reversible effect, contraception not sterilisation, as well as investigate whether there would be cumulative damage from repeated doses.

Link -via Popular Science | Photo: James Tsuruta and Paul Dayton