When we speak English, individual words often aren’t clear, they blend together. Less important words are quieter, and more important words are louder and longer. So you might say, “Iwannavisit my DAD in AUSTRALIA budditso EXPENSIVE!” The “I” is important grammatically, but it’s not important for meaning in conversation- it’s obvious it’s you. In some languages the “I” would be omitted altogether, but in English it’s there, just not very pronounced.
So my guess is, if the word’s not very important, it can be almost inaudible.
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