1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution so for 2 waves to be destructive, they need to be π , 3π, 5π... radians out of phase with each other. to get constructive, they have to be 0, 2π, 4π... out of phase. so to be constructive, the speaker needs to move 1π radian. we solve for the wavelength: 343 m/s divided by 615 Hz = 0.557 meters so the speaker just need to move 0.557 meters correct?