There are many attempts by music theorists to explain timbre more fully. Unfortunately, their ideas depend on the reader having an advanced knowledge of musical theory. The "Acoustical Society of America" (ASA) Acoustical Terminology definition 12.09 of timbre is "that attribute of auditory sensation which enables a listener to judge that two nonidentical sounds, similarly presented and having the same loudness and pitch, are dissimilar". It adds "Timbre depends primarily upon the frequency spectrum, although it also depends upon the sound pressure and the temporal characteristics of the sound". 