There is some connection between tongue position and the vowel chart, yes. But the connection to acoustics is far stronger, and much more widely-used. When people want to describe a vowel system rigorously, they don’t even bother attempting to describe the tongue shape — they just show a formant plot, assuming it shows the vowel space. (Sometimes they even superimpose a vowel chart directly on the plot.)Zju wrote: ↑Sun Sep 29, 2024 10:07 amChange in frequencies is due to change in vocal tract shape, no? Our tongues don't "draw out" perfect triangles or trapezoids when filling up the vowel space, but still lowering the tongue increases F1, and fronting it increases F2.bradrn wrote: ↑Sun Sep 29, 2024 8:57 amThis is the claim, yes. But in practice it’s false, and it’s been known to be false for ~40 years. You can consult Ladefoged and Maddieson’s Sounds of the World’s Languages for the details — there is no metric of tongue position which matches up well to the IPA vowel chart, whereas a plot of F1 vs F2 reproduces it almost perfectly.
(Or, if you don’t feel like digging up that book, read Geoff Lindsey’s article on the same topic.)
That source as well states that IPA vowel chart is based on tongue positions, even though they don't form a perfect geometric shape.
By contrast, descriptions of consonants don’t usually bother talking about acoustics. They just describe the articulation straightforwardly.