Question

Throughout the problem, take the speed of sound in air to be 343 m/s .

(Part A) Consider a pipe of length 80.0 cm open at both ends. What is the lowest frequency f of the sound wave produced when you blow into the pipe?
Express your answer in hertz.
(Part B) A hole is now drilled through the side of the pipe and air is blown again into the pipe through the same opening. The fundamental frequency of the sound wave generated in the pipe is now?
a. the same as before.
b. lower than before.
c. higher than before.

Answer 1

214.375 Hz, please check attachment for details.

Step-by-step explanation:

The speed of sound v = 343m/s and length of the pipe L = 80cm = 0.8m.

part(A)

The expression for fundamental frequency of an open pipe is

f = v/λ,

length of standing wave λ = 2 * L

= 1.6m

Thus fundamental frequency is

f = v/λ

= 343/(2*0.8)

= 214.375 Hz

part(B)

when hole is drilled through the side of the pipe, the frequency f is higher than before;

Since L decreases which decreases λ, v being the same! Hence f increases.