Tonal tongue, keen ears?

Thai phone booth‘It seems with a tonal language you can talk in a much lower volume than in European non-tonal languages. In the days before cell phones, in Bangkok, one of the noisiest cities of the world probably, there were phone booths where I could observe Thais chatting away, even on a cacophonous sidewalk on Sukhumvit Road.

When I tried to use the same phone booth in English, I had to shout at the top of my lungs. Maybe tones reduce the importance of the words’ other characteristics, like their phonetic contours.’

I received this interesting observation from a well-travelled American reader, Bill DeFelice. Could it be true that other phonetic features than tone are somewhat less vital in tonal languages, thereby allowing the speaker to reduce the volume? Or can his observation be explained in some other way? Perhaps Thai people are used to speaking at a lower volume, say for cultural reasons, and this habit may have honed their skill for picking up a signal amidst much noise. Or perhaps the Thai language has more redundancy than English, so that missing part of the signal is less fatal for understanding.

Or perhaps none of these ideas makes any sense at all – I’m speculating wildly here. But Bill observed what he observed, and we’re both curious what might be behind it. Suggestions, anyone?

Update: I’m told by linguist Mark Dingemanse that in research comparing twelve languages, including five tonal ones, he did not find any differences between them relating to noise and frequency of misunderstandings. This suggests that Bill’s observation requires some other explanation.