sound pressure vs instantaneous sound pressure

sound pressure and instantaneous sound pressure both are nouns.

Word	Noun	Adjective	Verb	Adverb
sound pressure	Yes	No	No	No
instantaneous sound pressure	Yes	No	No	No

As nouns, sound pressure and instantaneous sound pressure are synonyms defined as:

sound pressure and instantaneous sound pressure: the difference between the instantaneous pressure at a point in a sound field and the average pressure at that point

sound pressure (noun)	instantaneous sound pressure (noun)
the difference between the instantaneous pressure at a point in a sound field and the average pressure at that point	the difference between the instantaneous pressure at a point in a sound field and the average pressure at that point