"Simply phonetics. The science of speech. That's my profession; also my hobby. Happy is the man who can make a living by his hobby! You can spot an Irishman or a Yorkshireman by his brogue. I can place any man within six miles. I can place him within two miles in London. Sometimes within two streets. (1.118)"
Cacophony is the harsh mixture of sounds. This can be described as broken up dialect that may be hard to understand. In Pygmalion, Eliza Doolittle's harsh cockney accent would be an excellent example of cacophony. Eliza uses the slang and dialect from where she was brought up in, the slums, and it drastically impacts her life. She is unable to rise from her social class with her severe cacophony, which is why Higgins wants to train Eliza to speak in a proper English accent in the first place.