William Demant, the world's largest producer of hearing aids, said it could start producing cheaper over-the-counter hearing devices for the U.S. market if demand rises sharply once new legislation comes into effect.

Shares in William Demant and other hearing aid makers GN Store Nord and Amplifon plunged earlier this month after the U.S. Senate voted to approve the FDA Reauthorization Act which paves the way for over-the-counter (OTC) sale of hearing aids, among other things.

"I do not expect any significant change in the U.S. market, but should sales of products like these become substantial ... we will produce some as well," William Demant's CEO Soren Nielsen told Reuters by telephone.

North America, along with Europe, is William Demant's biggest market. Nielsen said that if the legislation comes into effect new players could quickly enter an already mature U.S. market for hearing aids where six producers currently compete.

The legislation still needs to be approved by President Donald Trump but is expected to go through and would allow the sale of OTC hearing aids without an audiologist being present in a bid to improve hearing aid accessibility in the United States.