A closed organ pipe has a fundamental frequency of 1.5kHz . The...

For a closed organ pipe, the resonate frequency(harmonics) is an odd multiple of the fundamental frequency.

Therefore, $\left(2n - 1\right){f}_{0} \le 20000Hz$, where $n = 1, 2, 3 . . .</p><p>${f}_{0} = 1 . 5kHz ⇒$fundamental frequency</p><p>Then,$n = 7$</p><p>The total number of overtones that can be heard is$6$. (${2}^{nd}$harmonic to${7}^{th}$harmonic. )</p></blockquote>$