Panel movement alone does not indicate audibly radiated sound.

Evidence

Mechanical and acoustical resonances can arise in the transducers, and in the enclosures of loudspeaker systems. Much ado has been made about mechanical resonances in loudspeaker enclosures, for good reason. They are large surfaces and can radiate significant sound if they move. When loudspeakers are measured in an anechoic chamber, or equivalent, and examined through 360° of rotation, any such radiated sound is captured, and, if significant, its presence will be noted. However, accelerometer measurements of the mechanical movement at a point on an enclosure surface is not definitive evidence of effectively radiated sound energy, or of its audibility. Some resonant modes in panels exhibit similar areas simultaneously moving in opposite directions. There is movement, but little sound is radiated. With scanning laser interferometers, it is possible to anticipate the sound radiating modes and provide selective stiffening or damping to address the problems. Brute force methods, like massively thick, heavy materials also work, of course, but elegant engineering can be effective and keeps cost and weight down. — Toole, Floyd E, Sound reproduction- the acoustics and…, 106

Categorization

• XREF: Connects to the general physics principle that net acoustic radiation depends on phase relationships across a surface, as in dipole vs monopole cancellation.