# Calibrated sine wave generator

1. Sep 18, 2014

### pHysicsN0OB

Imagine that you have a calibrated sine wave generator set at 900 Hz and you mix its signal with that of an uncalibrated generator also set at 900 Hz. You hear a beat frequency of 4 Hz.

What is the true frequency of the uncalibrated generator?
Is there more than one possibility?

I'm not sure where to begin

2. Sep 18, 2014

### Simon Bridge

Welcome to PF;
Hint: definition of "beat frequency": how do beats happen?
What is special about a calibrated wave generator compared with an uncalibrated one?

3. Sep 18, 2014

### pHysicsN0OB

Beats frequency happens when two different waves are at a point with the same amplitude.
A calibrated wave generator has a wave as a standard and an uncalibrated wave generated is not similar to the calibrated wave.

4. Sep 18, 2014

### pHysicsN0OB

Are these answers correct?

What is the true frequency of the uncalibrated generator?
The true frequency of the uncalibrated generator is 904 Hz.

Is there more than one possibility?
Yes. The uncalibrated generator could be 866 Hz,

5. Sep 18, 2014

### Simon Bridge

That is true, although the amplitude does not have to be the same, and there is another condition needed. But it is not the definition of the beat frequency.
i.e. how would you go about calculating the beat frequency - how is the beat frequency related to the frequencies of the two waves?

What does it mean to have a wave as a standard?
Note: you have answered the question "what is the difference between..." by saying "they are not similar"... that is called "begging the question".
In what way is the uncalibrated generator not similar to the calibrated one?
Specifically in terms of the frequency it emits compared with the frequency it is set to.

It looks like the first one is correct and the second is not.

6. Sep 18, 2014

### pHysicsN0OB

Thanks. The answer was already given to me in a different forum.

7. Sep 18, 2014

### Staff: Mentor

And being given the answer to your homework question helps you learn how to figure out future questions similar to this one? And helps you to learn how to figure out harder questions?

8. Sep 18, 2014

### KL7AJ

Yes, there are two solutions.

9. Sep 18, 2014

### Simon Bridge

@pHysicsN0OB: Perhaps you can show people here how it is done so your can help people who are stuck the same as you?