Regarding claims that helmets obstruct vision, studies show full-coverage helmets provide only minor restrictions in horizontal peripheral vision. A 1994 study found that wearing helmets restricts neither the ability to hear horn signals nor the likelihood of seeing a vehicle in an adjacent lane prior to initiating a lane change. To compensate for any restrictions in lateral vision, riders increased their head rotation prior to a lane change. There were no differences in hearing thresholds under three helmet conditions: no helmet, partial coverage, and full coverage. The noise typically generated by a motorcycle is so loud that any reduction in hearing capability that may result from wearing a helmet is inconsequential. Sound loud enough to be heard above the engine can be heard when wearing a helmet.