Someone posted a link to just that topic here. Apparently almost all languages transmit about 39 bits per second of data. Italians use 9 syllables per second, Germans only about 5-6, but both convey the same amount of information per second. But, not all syllables are equal. Japanese has about 5 bits per syllable, English has about 7 bits per syllable. The most information dense language per syllable is apparently Vietnamese with about 8 bits per syllable.

Apparently though, the bottleneck is the brain. The end result seems to be that languages that have fewer “bits of data” per syllable say those syllables more quickly, and the ones with fewer bits of data per syllable say those syllables more slowly, so that the average is about 39 bits per second no matter what the language.

Having said that, I often listen to podcasts sped up to 1.5x speed, and I listen to podcasts while doing other things, so I guess the bottleneck is probably on the sending side rather than the receiving side.