Basic Guidelines For English Spellings
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Annoyance, trouble; suffering, distress, sadness.
Middle English; earliest use found in Arthour and Merlin. Partly aphetic from annoy, and partly directly from Anglo-Norman nui, nouy, nuye.
A unit of perceived noisiness.
One noy is equal to the noisiness of a sound of specified bandwidth and intensity.
1950s. Shortened from noise.