1. Interference of Sound

2. Setup

3. Central Maximum Same distance to each speaker Start in phase
Constructive interference

4. First Order Maxima S S θ d } ΔS

5. In Phase l

6. If L>>d then the waves are almost parallel
Approximation
If L>>d then the waves are almost parallel θ d }

7. First Order Maxima S S θ d } ΔS

8. Equation for Maxima
m is the order of the maxima, so if m = 1 then they are called the first order maxima, m = 3 then they are the third order maxima, etc.

9. 180º Out of Phase

10. First Order Minima S X θ θ S d } ΔS X

11. Second Order Minima X S X S θ θ d } ΔS X X

12. Equation for Minima
If m = 0 then they are called the first order minima, m = 2 then they are called the third order minima, etc.

13. Beats

14. Definition
Periodic and repeating fluctuations heard in the intensity of a sound when two sound waves of very similar frequencies interfere with one another

15. Animation

16. Simulation

17. Calculating
The number of beats heard per second is simply the difference between the two frequencies.