A correspondent from Italy writes to ask if there is any connection betweeen speech and altitude. Do languages spoken in the mountains have a distinctive phonology?
I don't know of any correlation between speech and altitude environment - and, indeed, I wouldn't expect there to be any. I can't think of any reason why a sound system of a language should be affected by height or, for that matter, by any other physical environmental factor. I know there are popular views which argue to the contrary - for example, saying that people who live in mountains will have a higher and more sweeping range of intonation patterns, whereas people who live on low plains will have a flatter intonation, but phonetic investigations give no support. I've also come across such views in relation to the accents within a language (eg from dialect coach Joan Washington in a BBC4 TV programme earlier this year called 'How the Edwardians Spoke'). Another example is the belief that people who live in coastal districts have a lot of back consonants or a nasal twang because the sea mists cause more nasal catarrh - this has been claimed with reference to the Liverpool accent, for example. Again, there's no basis: back consonants and nasal twangs turn up in non-marine environments and lots of accents on coasts don't show these features.
The only language phenomena I can think of which relate to physical environment are the speech surrogate systems - the so-called 'drum or whistle languages', used to cope with the need to communicate across distances (such as mountain valleys). I give a brief account in my Cambridge Encyclopedia of Language, but there will be several references online.