Woon Ju Park, writing in Scientific American, describes new research on why people who lost their sight early in life often hear so well. The study, published in the Journal of Neuroscience, points to something called internal noise: how consistently the auditory system responds to the same sound over and over. Less internal noise means similar sounds are easier to tell apart.

The team tested nine people who became blind before age 2 and 18 sighted people, with a range of musical training in both groups. One task was detecting a tone in background noise, which shows how the inner ear handles different frequencies. The other was judging which of two tones was higher in pitch, which also depends on how the brain reads the sound.

The blind participants did better only on the pitch task, so the difference comes from brain processing and not from the ears. A mathematical model showed the gain came from reduced internal noise rather than sharper frequency tuning. Sighted musicians showed the same effect.…