In English, there are many combinations of writing for each sound.
The phonetic transcription of the dictionaries is very useful, but it is inaccurate.
And it is even worse when studying the sound "ɑ" since when listening to the pronunciations you can perceive that they do not always pronounce the same vowel. Since not everyone distinguishes between "ɑ" and "ɔ" and many other cases. And this survey was not done by anyone
You must be able to observe how the only vowels pronounced clearly are those marked "ˈ" (primary accent) or "ˌ" (secondary accent); the others are reduce them, which means that they produce them for less time, and tend to be only the sound that escapes when changing from consonant to consonant.
The other phenomenon that is difficult to accept but that it is necessary to master is to observe how the words in an expression are said together, what you can verify, when trying to listen only to the individual words with Praat.
In addition, you must incorporate into your language the use of contractions and idiomatic expressions.
For these reasons it is more convenient to start by learning each word individually and being you the only judge.

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