Researchers say they have found what could be a cheap, reliable, and long-lasting form of male birth control, although it involves zapping the testicles with ultrasound. A study on rats found that sound waves slowed sperm production to levels that would cause infertility in humans, making ultrasound a "promising candidate" for contraception, the BBC reports.
The researchers, who won a grant from the Bill and Melinda Gates Foundation, found that two 15-minute zaps delivered two days apart yielded the most effective results. They plan further studies to determine how long the contraceptive effect lasts—and to make sure it is reversible. The concept was first proposed in the '70s, when cancer patients due to have their testicles removed underwent the treatment and reported no pain, only a "gentle feeling of warmth."