For people with hearing loss, the sound signals from the inner ear to the brain will be weaker than normal, and it's possible that the brain amplifies these signals too much to compensate, resulting in hypersensitivity. However, this doesn't explain the cause in those with hyperacusis and no hearing loss.
Bicycle Valve Stem Types. There are three types of bicycle valve stems in use: Schrader, Presta and Woods/Dunlop. The Woods or Dunlop valve stem style is much more rare than the other two. Any wheel rim that fits a Schrader valve can also fit a Woods or Presta valve.
Calipers vs. Cantilevers. Bicycle rim brakes divide into two basic types: cantilever and caliper. Caliper brakes are self-contained mechanisms, attached to the bicycle's frame by a single bolt for each brake, front or rear. The arms reach downward from above the tire, and need to be long enough to get around the tire. Cantilever brakes attach to the sides of a bicycle's frame/fork, separately on each side.