# Homework Help: Calculating Beats

1. Nov 20, 2007

### BarCode

[SOLVED] Calculating Beats

1. The problem statement, all variables and given/known data

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?

2. Relevant equations

f = number of beats/time

3. 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.

2. Nov 20, 2007

### 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.

3. Nov 20, 2007

### BarCode

Ah, so I'd do

1000Hz - 998Hz = 2Hz

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

4. Nov 20, 2007

### 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.

5. Nov 20, 2007

### BarCode

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

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

6. Nov 20, 2007

### hage567

That's right.