What would we see if we had glasses that converted sound waves into light waves, assuming our brain became accustomed to them?
• If the glasses converted sound into light at proportional wavelengths or frequencies then you might be rather disappointed by the experience of “watching” music. Your ears can hear sound across nine or 10 octaves depending on your age. An octave is the interval between two notes where the frequency of the higher note is double that of the other: a piano typically covers more than seven octaves from lowest to highest key.
Your eyes on the other hand are sensitive to light with a frequency of between 400 and 790 terahertz, which is not even one octave. You would therefore be disappointed to find you could see less than a single octave of sound, maybe around middle C. The low notes of a piece of music would be “warm”, that is, well into the infrared, and the high notes would risk damaging your eyes as they would be ultraviolet.
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“Human eyes are sensitive to light with a frequency of 400 to 790 terahertz – not even one octave”
Pete Downing, Penicuik, Midlothian, UK
• Converting sound to light on a like-for-like basis would mean that sound waves of a high frequency (or pitch) would be converted to high-frequency light waves in the violet, blue and purple range.
High-intensity (loud) sounds would be converted to high-intensity (bright) lights. So an opera composed of high-frequency, high-intensity sounds would have bright lights varying from violet to blue or green. Low frequency, quiet noise, on the other hand would appear as dim light, changing from red to orange or yellow. A multitude of voices or other sounds would appear as a host of lights varying with the pitch and intensity of the sounds that created them.
Ruairi Atack, Dublin, Ireland
Readers might find our recent interview with artist Neil Harbisson (11 August, p 50) relevant to this topic too – Ed