Shouldn't one be make some sort of distinction  between phonological as opposed to phonetic representation.  Something like, same pronunciation different phonological rules.

  ----- Original Message ----- 
  From: David McCann<mailto:[log in to unmask]> 
  To: [log in to unmask]<mailto:[log in to unmask]> 
  Sent: 20 August 2008 14:53
  Subject: Re: Sibilants

  On Tue, 2008-08-19 at 00:59 -0500, Eric Christopherson wrote:

  > Is /D/ really different between American and UK English?

  According to Peter Ladefoged and Ian Maddieson (The Sounds of the
  World's Languages),

  "We investigated 28 native Californian college students and 28 British
  university students and staff… Nearly 90% of the Californian speakers
  produced θ … with the tip of the tongue protruded between the teeth…
  Only 10% of the British speakers made the sound this way; 90% of them
  used an articulation with the tip of the tongue behind the upper front

  J. C. Catford, who worked in Michegan, only described the dental
  articulation, so the interdental may be a Western thing. Any comments
  from the US?

  My speech is British (RP), but I'm one of the 10% with the interdental.