Question

If the velocity of sound in air is 336 m/s. The maximum length of a closed pipe that would produce a just audible sound will be

• A. 3.2 cm
• B. 4.2 m
• C. 4.2 cm
• D. 3.2 m

Answer 1

Answer: (B)

4.2 m

Answer 2

Minimum audible frequency

= 20 $Hz$

$\Rightarrow$ $\frac{v}{4l} = 20 \Rightarrow l = \frac{336}{4 \times 20} = 4.2m$