The jug trade
Whenever I’ve taught phonetics, I’ve been mildly uncomfortable about the fact that many if not most of the phonetics texts that I have to consult, even ones with a decided focus on English and relatively narrow transcriptions, don’t really note that /tr/ and /dr/ clusters are pronounced with an initial affricate of some sort (as opposed to a stop, that is). When I have seen some mention of this, the voiceless cluster is transcribed as [ʧr] and (more narrowly?) as [ʈʂɹ].
It’s such an easily observable phenomenon, and a student or two typically asks me about it before I have a chance to mention it in class myself. A wee small bit of the research on this phenomenon can be found with a quick web search (which I cite below the fold — if you know of more, please comment). Some of this research is concerned more specifically with the “retracted /s/” in /str/ clusters observed in some varieties of American English.
Unfortunately, there’s no standard way to test whether there’s an underlying /tr/~/ʧr/ contrast (or /d/~/ʤ/, in the voiced case) that is (nearly-)neutralized by this affrication. But President Bush committed a wonderful speech error in his State of the Union address earlier this evening that must say something about either the perception or the implementation (or both) of these clusters.

