threshold level vs intensity

threshold level and intensity both are nouns.

Word	Noun	Adjective	Verb	Adverb
threshold level	Yes	No	No	No
intensity	Yes	No	No	No

As nouns, intensity is a hypernym of threshold level; that is, intensity is a word with a broader meaning than threshold level:

threshold level: the intensity level that is just barely perceptible
intensity: the amount of energy transmitted (as by acoustic or electromagnetic radiation)

Other hypernyms of threshold level include intensity level, strength.

threshold level (noun)	intensity (noun)
the intensity level that is just barely perceptible	high level or degree; the property of being intense
	chromatic purity: freedom from dilution with white and hence vivid in hue
	the magnitude of sound (usually in a specified direction)
	the amount of energy transmitted (as by acoustic or electromagnetic radiation)