what's lost on many that cite such "speech intelligibility" studies (in an effort to imply speech intelligibility is improved with the presence of high-gain, early indirect specular reflections) is the context of such tests and their application. they are primarily with respect to UNAMPLIFIED environments such as classrooms, theaters, conference rooms, etc - where "speetch intelligibility" is "improved" by nature of the direct signal being "heard" where early reflections within the integration time increase the perceived loudness (gain) of the direct signal speech against the background noise floor.
user above cited:
https://asa.scitation.org/doi/abs/10.1121/1.1570439
it very-clearly outlines in the Abstract section that the context of the study is related to gain/snr issues - not articulation in amplified environments.
The speech intelligibility test results confirm the importance of early reflections for achieving good conditions for speech in rooms. The addition of early reflections increased the effective signal-to-noise ratio and related speech intelligibility scores for both impaired and nonimpaired listeners. The new results also show that for common conditions where the direct sound is reduced, it is only possible to understand speech because of the presence of early reflections.
in home reproduction environments, we have AMPLIFIED sound sources where if the gain of the direct signal cannot be "heard", one simply turns the volume knob appropriately. and if one has a condition where the amplified direct signal somehow CANNOT be heard without the increase in perceived gain due to early reflections, then one clearly has sound isolation issues and/or lives next to a construction site/train yard.
the 2nd article the user cited above :
https://www.google.com/url?sa=t&sou...Vaw0y-0tOmE_7ioJVIpsh5_pb&cshid=1586599059036
Speech intelligibility enhancement by early reflections:
Early reflections in a room can improve speech intelligibility for normalhearing
listeners, because the auditory system integrates them with the direct
sound which results in an increased speech level
again, not an issue in home reproduction setups that have amplification capability where the gain of the direct signal can easily be set such that the direct signal can easily be "heard".
these studies are far too commonly presented on audio forums but the context of the environments is usually lost or missed.
the easiest test to do at home is simply listen to a high-quality speech recording through headphones (of which there are no "early reflections"), and attempt to imply there is any sort of issue with speech articulation or intelligibility.