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Some Remarks About Beats. February 27, 2009 Look up beats in the textbook or in Measured Tones. Beats. When two tones f1 and f2 sound together, the resulting combination can sound good, bad or even horrible. If f1 and f2 are far apart, they may sound like two separate tones. - PowerPoint PPT Presentation
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Some Remarks About BeatsFebruary 27, 2009
Look up beats in the textbook or in Measured Tones.
Beats
•When two tones f1 and f2 sound together, the resulting combination can sound good, bad or even horrible.
•If f1 and f2 are far apart, they may sound like two separate tones.
•If they are an octave apart they will sound just fine.
•If they are very close to each other, the sound of audio beats will be heard.
Example: f2-f1=2 Hz.
http://qbx6.ltu.edu/s_schneider/physlets/main/beats.shtml
Adding Two Tones
Tone #1
Tone #2
Beat Period
N Peaks
N +1 Peaks
N Peaks
N +1 Peaks
21
21
)1(1
)1(
f
N
f
N
f
TNNTT
beat
beat
Tone-1
Tone-2
SomeAlgebra
)(
1
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)(
)1(
)1(1
)1(
121
12
1
112
12
21
21
fff
N
ff
fN
fffN
fNNf
f
N
f
N
f
TNNTT
beat
beat
)(
)(
11
12
1211
fff
and
fff
NNT
fT
beat
beatbeat
The beat frequency is thedifference between the frequencies
Two frequencies, 440 Hz. And 443 Hz. beat together. What is the beat frequency?
.sec31
.344044312
T
Hzff
A tuning fork has been damaged and its frequency slightly changed. What could its altered frequency be if it produces two beats per second with a tuning fork that is known to vibrate at 440 Hz?
• It could be 442 (442-440=2)• It could be 438 (440-438=2)
