How to Distinguish Perfect Fourth and Perfect Fifth in Ear Training

When two notes are sounded simultaneously you can often feel the perfect fifth interval. But you audiate the tones in your head, and you might be internally hearing the notes in your own vocal range, and you might have inverted them. So you imagine one note as the fifth on top, and the other note as the tonic below it.

Listen harder to what your ears are hearing. Is the fifth really the higher note? Then the interval is a perfect fifth. But if you concentrate and realize the “fifth” tone your ears are hearing is the lower note, then the interval is a perfect fourth.

Put another way, in terms of relative pitch, the interval from Do up to Sol is P5, but the interval from Sol up to Do is P4. In both cases you’re hearing Do and Sol, but it matters which one is the higher note and which is the lower one.