Two audio speakers are placed on a vertical rail. Speaker A is placed at head-level while Speaker B is place at some variable height, Δy, above Speaker A. Both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.880 meters. Calculate the lowest height that Speaker B can be placed above Speaker A to produce a minimum of sound heard by person standing Δx=6.38 meters directly in front of Speaker A.