1. Physics 101 Learning Object 2
Beat Frequencies at a Concert
One night, you and a friend decide to attend a concert. When, you arrive, you find it is not a very
popular artist, as you and your friend are the only two people in attendance. The only sounds
during the concert are coming from the guitarist, the bassist, and two separate generators in the
back of the room making high pitched noises. You soon find out why the band isn’t very
popular, as they aren’t very talented, so you turn your attention to something more interesting.
You wonder; if the difference in the frequencies of the notes of the guitar and bass, and the two
generators, are the same, will the beats you hear in a minute be the same from each? Does it
matter that the generators are of a significantly higher pitch than the two musical instruments?
Let’s say that in the concert, the guitarist holds his note for a minute at 147 hz, and the bassist
holds his note for the same amount of time at 135 hz. At the same time, one generator has a
frequency of 614 hz, and the other at 626 hz. you assume that there is no instrument/generator
interference.
Solution

2. The number of beats you hear in a given time is only determine by the difference in frequency,
not the magnitude of each. Therefore, you would hear the same amount of beats coming from
both the guitar and bass, and the two generators.
F1 - F2 = Delta F
Delta F x Seconds = Number of Beats
147-135 = 12 x 60 = 720 beats
626-614 = 12 x 60 = 720 beats