Attaching a small vibrating source to a larger surface boosts loudness by 25 dB.

Evidence

An experiment in the author’s study had the following results: the music box mechanism when played holding it firmly on top of a wooden desk was 25 dB louder than when it was played in the air, an intensity factor of 102.5 = 300. The sound from the vibrating tooth and bedplate is still present when the mechanism is attached to the desk, but completely masked by the much louder sound coming from the undulating desk surface. So it is with the violin: any weak sound coming from the vibrating string is vastly overpowered by the sound emanating from the vibrating violin body, and, as we shall see, the air oscillating in and out of the f-holes. — Eric J. Heller, Why You Hear What You Hear- An…, 723

Categorization

• XREF: Concrete quantified example of the impedance-matching principle from paragraph 722; the 300-fold intensity gain is the load-bearing number.
• SEED: A contrarian sensory fact: a surface vibrating a billionth of a meter is heard far louder than a source vibrating 100,000 times more — good hook for an essay on why size, not energy, governs what we hear.