Resonant reflections raise impedance in throats and reproducers

Evidence

There are several other ways to see how more power is extracted from the source under resonant conditions. One is the method of images, introduced in section 7.2, which shows that in certain cases the sound field in the presence of walls is as if there were additional sources of sound with no walls. Another pathway is to examine the work done by the source: the reflected in-phase amplitude causes the source to push against a slightly time-delayed echo. As a result, it does more work against additional external force. The resistive part of that work leads to sound production. In engineering circles, you would be likely to hear (quite correctly) that the impedance is higher in throats and reproducers, allowing a better impedance match with a high-impedance source such as the membrane to which the needle is connected. The reason the impedance is higher is again the many reflections. — Eric J. Heller, Why You Hear What You Hear- An…, 887

Categorization

• XREF: The impedance-matching explanation echoes the Milgrom law-merchant material on how institutions improve matches — and connects to classic electrical-impedance analogies in acoustics.