The various modes of vibration in the form of displacement and pressure waves
(i) First mode of vibration : In this mode of vibration
This frequency is called first harmonic or fundamental note.
(ii) Second mode of vibration : In this mode of vibration
(iii) Third mode of vibration : In this mode of vibration
This frequency is called second overtone or fifth harmonic.
Hence different frequencies produced in a closed organ pipe are in the ratio 1 : 3 : 5 : .......... i.e., only odd harmonics are present in a closed organ pipes.
