A speaking horn’s distant source location distorts vowel-forming resonances

Evidence

Although we do not have all the tools at our disposal, we set the stage regarding a subtlety about speaking horns or trumpets. A speaking trumpet uses the vocal folds, a source of sound 15 or 17 cm inside the vocal tract, not right at the throat of the horn, where horn loudspeakers put the source. Buzzing lips would put the source in the throat and amplify it. The resonances of the vocal tract are needed to form vowels, and the horn connected to the mouth would modify them, by changing the impedance mismatch at the lips. The more the impedance is matched there, the more the resonances might be distorted. — Eric J. Heller, Why You Hear What You Hear- An…, 558

Categorization

• XREF: Directly explains the historical talking-horn artifacts studied in the book’s context; bears on why ancient ‘megaphone’ trumpets could not preserve speech intelligibility.
• QUESTION: Do modern megaphones and loudspeaker horns suffer this same vowel distortion, and how is it mitigated?