According to the map created by Aschmann, a linguist by hobby, some unusual vowel sounds are used in the area of Greater New York City. As illustration, Aschmann explains how "bad" and "had" don't rhyme thre. Rather, "bad" is phonetically closer to "bared"! The reason, he explains is that in this area there's a systematic tendency for r-dropping.

People in the Greater New York City region, as well as in Eastern New England (ENE), Australia, and other former British colonies, use distinct sounds when it comes to pronouncing the words "bother" and "father." Apparently, these regions do not fall in the bother/father merger category where the first vowels in each word are pronounced the same.

Apart from the regions mentioned, the rest of the US, with only a few exceptions, uses the same vowel for many other word pairs, such as "Saab" and "sob," or "con" and "Kahn."

This is a linguistic feature that's more emphasized in the Southern states in America. The pin/pen merger suggests that words like "Ben" and "bin," "pin" and "pen," or "hem" and "him" are homonyms (words that sound alike) even though the vowels are different in each member of the word pairs. What's even more confusing about the pin/pen homonymy is that there's no clear-cut distinction where this tendency is present.

According to Aschmann's painstaking research, it is a distinctive Southern accent trait, but it is gradually influencing northern dialects and accents too. In fact, the pin/pen homonymy is found in California and other areas, often where citizens from Oklahoma and Texas now reside.

Another American English distinctive homonymy is that of words such as "Tom," "cot," and "don" using the same vowel sound as words such as "caught," "Dawn." and "paw." Western states tend to exhibit this merging while Southern states have different vowels for each of these word pairs.

A few areas reported by Aschmann tend to preserve a pronunciation difference between the words "Mary," "marry," and "merry."

The typical - if there's such a thing - American accent doesn't distinguish between these sounds. The distinction can be found in New York and Boston, a phenomenon due to r-dropping. However states such as Philadelphia and other Eastern regions also have different sounds for these three words, something linguists are still baffled by!