There is indeed a noun affect, which I didn't find out until I got to college and did some study of the psychology of music. The noun affect means "an expressed or observed emotional response."
While either noun could be used correctly, I would use effect. The term for effect is idiomatic and generally understood, and the use of affect as a noun is very rare, generally limited to textbooks on psychology.
Here are the different meanings of affect and effect:
Effect as a noun: something that is produced as a result or a consequence of something else. The loud noise had an effect on my hearing.
Effect as a verb: to cause to happen. By climbing down a tree by the window, I effected my escape from the burning house.
Affect as a verb: to have an effect on something. The loud noise affected my hearing.
Affect as a noun: already explained above. "Emotion or affect is aroused when a tendency to respond is arrested or inhibited." (Leonard B. Meyer, Emotion and Meaning in Music, University of Chicago Press, 1956.)