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Beat Frequency LO 8

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Kathy Macarayan

Beat frequency occurs when two sounds waves of slightly different frequencies are combined, resulting in a fluctuating volume caused by the interference between the waves. The difference between the frequencies is called the beat frequency, which can be used to tune instruments by listening for beats. The beat frequency formula is fbeat= |f1 - f2|, where f1 and f2 are the frequencies of the two sources. An example problem demonstrates how to use the beat frequency to calculate the pitch of a piano note based on the number of beats heard when played with a tuning fork.

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BEAT FREQUENCY Kathy Macarayan
WHAT IS A BEAT FREQUENCY IN SOUND? The sound of a beat frequency or beat wave is a 鍖uctuating volume caused when you add two sound waves of slightly different frequencies together. If the frequencies of the sound waves are close enough together, you can hear a relatively slow variation in the volume of the sound. A good example of this can be heard using two tuning forks that are a few frequencies apart. Ron Kurtus, October 2013 (http://www.school-for-champions.com/science/ sound_beat_frequencies.htm#.VQZWZUJupFI)
APPLICATIONS OF BEAT FREQUENCY The phenomenon of beats is most renowned for its in鍖uence in tuning instruments.When two frequencies are played simultaneously, instruments are tuned to match the correct frequency of the note; in other words, you are listening for beats. When beats can no longer be detected, the instrument is in tune.
BEAT FREQUENCY FORMULA Beat frequency can be solved by using the equation fbeat= | f1 -f2 | where f1 and f2 are the frequencies of the two sources
THE BEAT ENVELOPE If you add two waves of slightly different frequencies, the resulting amplitude will vary or oscillate at a rate that is the difference between the frequencies. That beat frequency will create a beat envelope around the original sine wave. Ron Kurtus, October 2013 (http://www.school-for-champions.com/science/ sound_beat_frequencies.htm#.VQZWZUJupFI) F1 (slightly slower frequency) F2 (slightly faster frequency) Because the frequencies are so close, you would hear a frequency that is the average of the two as well as the modulation of the amplitude as the beat frequency de鍖ned by the previous formula.
EXAMPLE A tuning fork with a frequency of 560 Hz is sounded together with a note played on a piano.Twelve beats are heard in 4 seconds.What is the frequency or pitch of the piano note?
SOLUTION First, you must 鍖gure out how many beats are heard per second Beats per second = 12 beats/ 4 seconds = 3 Hz
SOLUTION Second, use the beat frequency formula to solve fbeat= | f1 -f2 | 3 Hz = |560 Hz- f2| There are two possible answers, f2= 557 Hz, 563 Hz
MORE HELP If you are still confused about beat frequency, check out this helpful youtube video by Brightstorm https://www.youtube.com/watch? v=ylBne5guWOc&spfreload=10
THANKS FOR WATCHING
Images: http://www.taylorguitars.com/sites/default/files/hero-acoustic-guitars-browse-by-wood-taylor-guitars.jpg http://avstrings.com/sites/default/files/imagecache/fullscreen/Metal%20Tuning%20Fork%20with%20Wood%20Block.jpg http://www.uaudio.com/media/blog/2012/05/tune_hero.jpg

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Beat Frequency LO 8

  • 2. WHAT IS A BEAT FREQUENCY IN SOUND? The sound of a beat frequency or beat wave is a 鍖uctuating volume caused when you add two sound waves of slightly different frequencies together. If the frequencies of the sound waves are close enough together, you can hear a relatively slow variation in the volume of the sound. A good example of this can be heard using two tuning forks that are a few frequencies apart. Ron Kurtus, October 2013 (http://www.school-for-champions.com/science/ sound_beat_frequencies.htm#.VQZWZUJupFI)
  • 3. APPLICATIONS OF BEAT FREQUENCY The phenomenon of beats is most renowned for its in鍖uence in tuning instruments.When two frequencies are played simultaneously, instruments are tuned to match the correct frequency of the note; in other words, you are listening for beats. When beats can no longer be detected, the instrument is in tune.
  • 4. BEAT FREQUENCY FORMULA Beat frequency can be solved by using the equation fbeat= | f1 -f2 | where f1 and f2 are the frequencies of the two sources
  • 5. THE BEAT ENVELOPE If you add two waves of slightly different frequencies, the resulting amplitude will vary or oscillate at a rate that is the difference between the frequencies. That beat frequency will create a beat envelope around the original sine wave. Ron Kurtus, October 2013 (http://www.school-for-champions.com/science/ sound_beat_frequencies.htm#.VQZWZUJupFI) F1 (slightly slower frequency) F2 (slightly faster frequency) Because the frequencies are so close, you would hear a frequency that is the average of the two as well as the modulation of the amplitude as the beat frequency de鍖ned by the previous formula.
  • 6. EXAMPLE A tuning fork with a frequency of 560 Hz is sounded together with a note played on a piano.Twelve beats are heard in 4 seconds.What is the frequency or pitch of the piano note?
  • 7. SOLUTION First, you must 鍖gure out how many beats are heard per second Beats per second = 12 beats/ 4 seconds = 3 Hz
  • 8. SOLUTION Second, use the beat frequency formula to solve fbeat= | f1 -f2 | 3 Hz = |560 Hz- f2| There are two possible answers, f2= 557 Hz, 563 Hz
  • 9. MORE HELP If you are still confused about beat frequency, check out this helpful youtube video by Brightstorm https://www.youtube.com/watch? v=ylBne5guWOc&spfreload=10