Adjacent surface compressions and rarefactions can cancel sound before it radiates.

Evidence

Surfaces have modes that, like a string, undulate sinusoidally in time. As a surface undulates in such a mode, it deforms outward at one place, and simultaneously inward at an adjacent location. This means adjacent rarefactions and compressions will short-circuit, if these opposing regions are closer together than a half-wavelength of the sound at the frequency of the surface waves. In the short-circuit mechanism, air flows from high pressure to low pressure before the sound has a chance to radiate away. — Eric J. Heller, Why You Hear What You Hear- An…, 669

Categorization

• DEFINE: Introduces the ‘short-circuit mechanism’ — the key concept behind why surface wave speed dictates radiated loudness.