sone

A subjective unit of loudness, as perceived by a person with normal hearing, equal to the loudness of a pure tone having a frequency of 1,000 hertz at 40 decibels.

An old spelling of soon.

a subjective unit of loudness for an average listener equal to the loudness of a 1000-hertz sound that has an intensity 40 decibels above the listener’s own threshold of hearing

a unit of perceived loudness equal to the loudness of a 1000-hertz tone at 40 dB above threshold