Why does "don't be" sometimes sound like "dombe"?

Question

Why does "don't be" sometimes become "DOMBE"? There is no M in the spelling then why?

Answer 1

Short answer

Some people pronounce Don't be as dombe because the t is sometimes deleted and the n is assimilated to an m in anticipation of the following b.

Explanation

In Don't be, the /t/ is flanked by two consonants (/n/ and /b/) and in normal or casual speech, some people tend to drop some consonants (such as /t/ and /d/) when they come between two other consonants. The process of deletion is called elision. So when pronouncing don't be in casual speech, the /t/ is sometimes elided:

• Don't be [ˈdəʊntbiː] → don be [ˈdəʊnbiː]

Another process involved here is assimilation which makes nearby sounds similar. Adjacent sounds often influence each other so they become more similar (assimilated). For instance, the n in ten pies is likely to be pronounced /m/ in anticipation of the following bilabial stop—/p/.

After the elision of the /t/, we're left with:

• don be [ˈdəʊnbiː]

The nasal /n/ in don be is likely to assimilate to a /m/ in

• don be [ˈdəʊnbiː] → dombe [ˈdəʊmbiː]

That's why some people pronounce it dombe.

Other examples of assimilation include:

• handsome → pronounced hansom
• mission, vision, treasure etc
• assume pronounced ashoom
• handbag pronounced hambag etc.