If you put your finger on the midpoint of A-110 on a guitar string what do you hear?

If you put your finger on the midpoint of A-110 on a guitar string what do you hear?

• A. The next higher A, A-220
• B. The same A-110
• C. The next lower A, A-55
• D. A C-sharp interval

Answer: (A)

Touching the string at its midpoint creates a node there, so the string can’t vibrate in its fundamental mode across the whole length. Instead, it behaves as two equal vibrating halves, and each half can vibrate at twice the original frequency. Doubling the frequency of the A string tuned to 110 Hz gives 220 Hz, which is the A one octave higher. So you hear the next higher A, not the same pitch, not a lower pitch, and not a different interval.

Touching the string at its midpoint creates a node there, so the string can’t vibrate in its fundamental mode across the whole length. Instead, it behaves as two equal vibrating halves, and each half can vibrate at twice the original frequency. Doubling the frequency of the A string tuned to 110 Hz gives 220 Hz, which is the A one octave higher. So you hear the next higher A, not the same pitch, not a lower pitch, and not a different interval.