I created the survey to answer a question which arose in conversation with a British English speaker about the number of vowels in American English and my Canadian brain could not cope with ‘fox’ and ‘dog’ having different sounds.
To hear the target vowels, go to this site, scroll down & click on the /ɒ/, /ɑ/ and /ɔ/ on the bottom right of the vowel diagram. Some North American speakers say the /ɔ/. All say either or both of /ɒ/ & /ɑ/. Most British English speakers say all three.
Because my vowels are so lacking in variety, I’ll use sets of words from J.C. Wells’ Accents of English to illustrate the results of the survey. See this site for a great explanation of vowel categories.
North American English speakers can sort the first 4 groups of words on the chart below into 1 or 2 sounds. Many, but not all, British speakers can sort all 7 groups into the 3 sounds.
Survey responses included: 40 England, 32 Canada & 60 US. The sample from the northeast US was small (6) but has been included in the final numbers. The results do not capture variations within regions but do capture broad and significant differences for teaching spelling.
There was variation between the Northeast and Southern accent responses but it was largely agreed that they have two distinct sounds where the rest of the country has one. Again, this does not mean that ‘hawk’ sounds exactly the same in New York and Fort Worth, just that the vowel sounds in ‘hawk’ and ‘stop’ sound different in both places.