This is a picture of the sound "be". Click to listen.
This is a picture of the sound "pee"
Can you see a difference at the start of the sound?
"pee" starts with a little "explosion" as the lips open and the air in your mouth escapes. Then there is a quiet part before the sound of the vowel "eee" starts.
When we say "be", the vocal cords are already together and ready to vibrate when your lips open, or even a little before:
Can you see the little bit of sound before the explosion?
Here are some animations of people saying "pa" and "ba":
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