March 6 World Health Organization warning: daily use of personal audio devices (such as smartphone headphones) should not exceed 1 hour, listening to the process should avoid high volume and preferably have a short break; or in noisy places (volume more than 100 decibels) should not exceed 15 minutes, available ear plugs (noise mitigation) or noise-canceling headphones. Hair dryers or subway noise can reach 100 decibels.