This is rather neat. They evaluated acoustic
performance of calls played over distances
in a savannah like environment.

https://www.nature.com/articles/s41598-023-48165-7
Published: 21 December 2023

Open plains are not a level playing field for
hominid consonant-like versus vowel-like calls

Abstract

Africa’s paleo-climate change represents an
“ecological black-box” along the evolutionary
timeline of spoken language; a vocal hominid
went in and, millions of years later, out came
a verbal human. It is unknown whether or how a
shift from forested, dense habitats towards
drier, open ones affected hominid vocal
communication, potentially setting stage for
speech evolution. To recreate how arboreal
proto-vowels and proto-consonants would have
interacted with a new ecology at ground level,
we assessed how a series of orangutan voiceless
consonant-like and voiced vowel-like calls
travelled across the savannah. Vowel-like calls
performed poorly in comparison to their
counterparts. Only consonant-like calls
afforded effective perceptibility beyond
100 m distance without requiring repetition,
as is characteristic of loud calling behaviour
in nonhuman primates, typically composed by
vowel-like calls. Results show that
proto-consonants in human ancestors may have
enhanced reliability of distance vocal
communication across a canopy-to-ground
ecotone. The ecological settings and
soundscapes experienced by human ancestors may
have had a more profound impact on the
emergence and shape of spoken language than
previously recognized.

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