Which harmonic occurs a third above the 3rd harmonic?

To determine which harmonic occurs a third above the 3rd harmonic, it's essential to understand the relationship between harmonics in a harmonic series. The harmonic series is built on whole-number multiples of a fundamental frequency.

The first harmonic is the fundamental frequency itself (often referred to as the 1st harmonic), the second harmonic is an octave above that (2 times the frequency of the fundamental), and the third harmonic is a perfect fifth above the second harmonic (3 times the frequency of the fundamental).

When identifying a harmonic that is a third above the 3rd harmonic, we calculate this in reference to the frequency of the 3rd harmonic. Since the 4th harmonic follows the sequence directly, it is calculated as 4 times the fundamental frequency, which is a major third above the 3rd harmonic. Thus, the 4th harmonic indeed occurs a third above the 3rd harmonic in the harmonic series.

This understanding establishes the 4th harmonic as the correct answer, as it aligns with the interpreted frequencies from the harmonic series.