Regional speech patterns or just laziness?

[flamingdem]

82. The "th" sound and the lazy theory

dat's classy it's not wachoo tink.

http://dialectblog.com/2011/04/12/th-in-city-accent/

–In the accents of New York City, Chicago, and Philadelphia, among many other American cities, this becomes a dentalized ‘d‘ or ‘t‘ sound. Hence the famous (albeit inaccurate) caricature of New Yorker’s pronouncing 33rd Street as ‘toydy toyd shtreet.’

–In London, voiced th often becomes ‘d‘ at the beginning of a word: this becomes ‘dis.’ Meanwhile voiceless th becomes ‘f;’ mouth therefore is pronounced ‘mouf.’

–In Dublin, th simply becomes plain old ‘t‘ and ‘d:’ ‘ting,’ ‘dis,’ etc.*

Obviously, not all cities have this funny business with th. But there are enough instances of this happening that I see a slight correlation between urban areas and accents with non-standard th pronunciations.

What accounts for this? The most obvious explanation is that all of these cities have been subject to quite a bit of immigration. Since standard English th (θ or ð) exists in few languages, many people who speak English as a second language use alternate pronunciations. And this may have filtered down into the speech of native English speakers.

An even simpler explanation may be at play, though: th is frankly a cumbersome sound. I’ve been speaking English for my entire life, and I still occasionally stumble over this consonant. There is a reason young children have no problem pronouncing ‘m‘ in mama, but tend to say ‘mouf’ when they mean mouth. Linguists will send me hate mail for saying this, but I find something inherently unnatural and awkward about English th.