How Many Beats Will Be Heard in 10 Seconds with Frequencies of 1000Hz and 998Hz?

[BarCode]

[SOLVED] Calculating Beats

Homework Statement

A person has two audio frequency generators with which to demonstrate beats. One generator is set to 1000Hz and the other to 998Hz. How many beats will be heard in 10s?

Homework Equations

f = number of beats/time

The Attempt at a Solution

number of beats = time/f
= 1000Hz/10s
= 100Hz

number of beats = time/f
= 998Hz/10s
=99.8Hz

Then I subtracted the two, getting 0.2 beats, which is most utterly wrong.

 

[hage567]

Why are you dividing the frequencies by 10 before you subtract? You want to find the differences in the frequencies to figure out the beat frequency. Once you know the beat frequency, you can figure out how many beats there are in 10 seconds.

 

[BarCode]

Ah, so I'd do

1000Hz - 998Hz = 2Hz

beats = 2Hz/10s (rearranged f = b/t to b = f/t)

 

[hage567]

That's not right, that's the same answer you just had. What's the definition of frequency? Check your units to see if you think they make sense.

 

[BarCode]

Ah I see where my rearrangement went wrong, it should be

Beats = frequency * time
so...
beats = 2Hz * 10s
= 20 beats

 

[hage567]

That's right.