💯 Analysing Sound Hertz | Sound Frequency | Questions

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Timeline:
0:00 Intro
0:20 Question 6 Finding Frequency
1:15 Question 7 Finding Period
1:44 Question 8 Comparing Flute and Tuba
2:28 Question 9 Frequency and Octave
4:12 Question 10 Octaves and Wavelengths

Questions 6

A certain violin string vibrates back and forth 640 times every second when it is plucked or bowed. What is the frequency of the sound that it produces?

(A) 320 Hz
(B) 640 Hz ←
(C) 1.56 ms
(D) 3.13 ms

Frequency is measured in Hz.
These are measurements of the period.
The sound produced has the same frequency as its source.

Question 7

The A below middle C has a frequency of 220 Hz. What is this musical note’s period?

(A) 2.3 ms
(B) 3.9 ms
(C) 4.5 ms ←
(D) 9.1 ms
The period of a note is given by T = 1/f.

Question 8

In terms of frequency, compare the music produced by a flute to that of a tuba.

The flute produces music with a much higher pitch than music produced by a tuba. Sounds with higher pitches also have higher frequencies, so the flute produces music with higher frequencies than music produced by a tuba.

Question 9

Suppose the note “Middle C” has a frequency of 256 Hz.

(a) Calculate the frequency of the C that is one octave above middle C.

A difference of one octave equates to a doubling of the frequency.
256 x 2 = 512 Hz

(b) Calculate the frequency of the C two octaves above middle C.
512 x 2 = 1024 Hz

Question 10

A student uses an oscilloscope to measure the wavelengths of two musical notes in the same medium. How will their wavelengths differ if the two notes are one octave apart?

The velocity of sound depends on the medium, so if both waves travel through the same medium, they will have the same velocity. From the equation, this means that the higher note (which has twice the frequency of the lower note) has a wavelength half as long as, the lower note.