Airlines including Delta, United and Southwest, as well as the Association of Flight Attendants (AFA), share their rules when it comes to using headphones on an airplane.

Around one billion young people worldwide could be at risk of hearing loss from listening to headphones or attending loud music venues, a large review of the available research estimated on Wednesday.

However, a growing number of cases are emerging in people outside these groups, sparking concerns that noise canceling headphones may be to blame. The act of blocking out everyday sounds could ...