Since enharmonic notes sound exactly the same, some intervals have different names. C to F# and C to Gb are two different intervals that sound exactly the same. While the two intervals can be visually identified, they cannot be distinguished aurally.

On aural only exercises call this tritone interval a diminished fifth.

Today's Interval Dictation has sixteen visual and aural examples that contain Perfect 4ths, Augmented 4ths, diminished 5ths and Perfect 5ths.