c) Humans are able to make sense of sounds at a much higher pitch than previously thought.
a) A note has a fundamental tone- the pitch we hear- and a series of overtones that occur at higher frequencies. Overtones are what give a sound its timbre, and enable us to distinguish an oboe from a trumpet from its sound alone.
d) Previous studies have shown that humans are unable to recognise melodies whose notes have a fundamental tone above 5 kilohertz.
e) It was thought that, at frequencies this high, the rapidly cycling sound wave was too fast for the auditory nerve to cope with. To test this theory, Andrew Oxenham and his colleagues at the University of Minnesota in Minneapolis asked a group of six students whether two four-note melodies were identical or not. As in previous studies, the volunteers could not recognise melodies with fundamental tones above 5 kHz.
b) The team then took a fundamental tone pitched below 5 kHz and digitally filtered it to leave just the overtones above 6 kHz. Surprisingly, the volunteers were able to distinguish these melodies.
