Horn confinement forces air bursts to do more acoustic work

Evidence

Sirens can be extremely loud, especially when located at the throat of a horn. The horn, as we know, acts to extract much more energy from a source, here an emerging burst of air. Each burst is forced by the horn confinement to do more work against its own pressure (proximity resonance). The horn directs the sound energy and, if large enough, releases it without reflection at the end. — Eric J. Heller, Why You Hear What You Hear- An…, 584

Categorization

• XREF: Builds directly on chapter 2’s horn/proximity resonance discussion of how horns extract energy from a source.
• DEFINE: Explains proximity resonance as bursts forced to work against their own pressure by horn confinement.