You hear a beat produced by 2 sources: 342.6 and 351.8 Hz. What is the period of the resulting beat tone? -- is there a formula for this? If so what is it and how do you solve the question?
beats occur in nonlinear mediums, you get the sum, and the difference frequency. Often, we just look at the difference frequency as the beat...here it is 351.8-342.6=9.2hz
period then is 1/9.2 seconds