Throat chamber echoes raise impedance by in-phase amplitude buildup

Evidence

The impedance is raised in the throat of a horn because of the nearly instant reflections, or echoes, from the walls of the throat chamber; these echoes linger in the throat, increasing the pressure against which the sound just entering has to work. The result is that sound amplitude is still being added in phase with amplitude that has been added just a moment before and has reflected once or several times off nearby walls. In chapter 9, we will see that resonance is defined in terms of the constructive addition of amplitude at a source. Without the walls present, the source amplitude will escape, and new pressure fluctuations would have nothing to constructively interfere with. — Eric J. Heller, Why You Hear What You Hear- An…, 544

Categorization

• DEFINE: Defines resonance as constructive amplitude addition at a source caused by lingering wall reflections.
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 544
• XREF: connects to: Acoustic impedance mismatch determines both reflection phase and magnitude; Impedance mismatch determines whether a sound pulse reflects or passes; Echo interference creates sinusoidal power fluctuations that average to zero

Broader Connections

• Acoustic impedance mismatch determines both reflection phase and magnitude #corroborates (0.80)
• Impedance mismatch determines whether a sound pulse reflects or passes #corroborates (0.75)