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1. Beats in Music Gillian Trotter Physics 101 203
2. What is a beat? When two waves of similar amplitude, but
different frequency interfere, there is a resulting wave. The
resultant wave has a fluctuating amplitude, due to areas of
constructive and destructive interference.
3. What is a beat? By definition, a beat is a periodic
variation of sound or amplitude due to the combination of two waves
having similar but not identical frequencies.
4. What do beats actually sound like?
https://www.youtube.com/watch?v=V8W4Djz6jnY
5. What do beats actually sound like? In the video on the
previous slide, the pulsations that could be heard when both tuning
forks were struck were the beats! The two waves were interfering
and creating different resultant amplitudes.
6. What do beats actually sound like? In the next video, we can
see on a visual app how the resultant amplitude of two similar
frequencies is the same. However, as the frequency of one of the
sine generators is changed, a difference in amplitudes can be seen
and heard. As the disparity between the two frequencies increases,
the number of beat frequency also increases.
7. What do beats actually sound like?
https://www.youtube.com/watch?v=I9f6bP3x_yo
8. Beat Frequency In the last video we heard that as the
difference in angular frequency between the two waves increased, so
did the beat frequency. Beat frequency is the number of pulsations
heard in one second when two sound waves of different frequencies
interfere.
9. Beats in Music Beats are especially important in music.
Different beat frequencies can be heard when instruments are being
tuned, like at the beginning of an orchestral performance.
10. Tuning The tuning of most stringed instruments is done
using an electric tuner, but pianos used to be tuned with tuning
forks. A key would be played, the hammer would strike the string,
and a tuning fork would be struck at the same time. A note was in
tune when the beat frequency was heard to be zero.
11. Tuning Tuning a stringed instrument is usually done by
increasing or decreasing the tension in the strings. When we think
about this mathematically, this is because v = and v = (T/)
Therefore = (T/) As tension is altered, so is frequency.
12. A Question About Beat Frequency An A (440 Hz) is played on
the piano at the same time as a tuning fork of 446 Hz is struck. 1.
What is the beat frequency you hear? 2. How many beats will be
heard in one second? 3. How many beats will be heard in 10
seconds?
13. Answers 1. What is the beat frequency you hear? The beat
frequency is equal to the difference between the two frequencies
being played. To solve this question we simply have to subtract 440
Hz from 446 Hz, with the result being 6 Hz. 2. How many beats will
be heard in one second? The number of beats heard in one second is
equal to the beat frequency. This is because the measurement of Hz
is actually equal to s-1. Therefore the answer is 6 beats per
second, or 6 beats s-1. 3. How many beats will be heard in 10
seconds? Since we know how many beats are produced in one second,
we can multiply 6 beats/second by 10 seconds to obtain 60
beats.