Sympathetic plate vibration requires correct phase and location matching

Evidence

When the lower one is set into vibration with a bow, holding the upper one above it induces the same pattern at the same frequency, especially if it is held close and above, as shown in this figure. That way, both the driving frequency and the forcing pattern are ideal to get the second plate into sympathetic vibration, as the pressure variations are communicated via sound with the correct phase and at the correct locations on the second plate. — Eric J. Heller, Why You Hear What You Hear- An…, 1401