Question

How many frequencies below `1 kH_(Z)` of natural oscillations of air column will be produced if a pipe of length `1 m` is closed at one end? [ velocity of sound in air is `340 m//s`]
A. `3`
B. `6`
C. `4`
D. `8`

Answer 1

Correct Answer - B
Fundamental frequency,
`f_(o) = (nu) / (4l) = (340) / (4xx1) = 85 H_(Z)`
Six frequencies can be produced below `1 kH_(Z)` .
Those six frequency are , `f_(o)`, `3 f_(o)`, `5 f_(o)`, `7 f_(o)`, `9 f_(o)` and `11 f_(o)`.
As `13 f_(o) = 1105 H_(Z) gt 1000 H_(Z)` or `1 kH_(Z)` .