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Chapter 10
Hearing Lab 4
To the Instructor: This is designed to help the student identify the relationship between period
and frequency.
Frequency and Period
To measure period in acoustics, you must be able to see the waveform.
1. Identify the period of the following waveform. To do this, first identify one cycle and then
measure the period using the scale given next.
A
M
D
E
-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
time (msec)
Now calculate frequency of that wave. Remember that f = 1/T, where f is frequency and T is
period (in seconds).
a. ________ period in milliseconds (from measurement)
b. Divide period (above) × 1000 to get seconds:
T = ________/1000 = ________ seconds
c. Now calculate frequency: f = 1/T; f = 1/_______ = _________
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2. Identify the period of the following waveform. To do this, first identify one cycle and then
measure the period using the scale given next.
A
E
-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
time (msec)
Now calculate frequency of that wave. Remember that f = 1/T, where f is frequency and T is
period (in seconds).
a. ________ period in milliseconds (from measurement)
b. Divide period (above) × 1000 to get seconds:
T = ________/1000 = ________ seconds
c. Now calculate frequency: f = 1/T; f = 1/_______ = _________
3. Identify the period of the following waveform. To do this, first identify one cycle and then
measure the period using the scale given next.
Calculate a couple more of these for practice:
T f
a. 10 msec _________ Hz
b. 20 msec _________ Hz
In that case, do the reverse: T = 1/f, where T is period (in seconds), and f is frequency. In this
case, we’ll get T in seconds, but we want to convert to milliseconds to keep everyone happy.
Given f = 120 Hz
T = 1/120 = ______ seconds;
T × 1000 = msec, so T= _______ × 1000 = _______ msec
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Calculate a few of problems deriving period from frequency.
f T
a. 630 Hz ________ msec