Here's why:
* Place of articulation: Both "b" and "p" are bilabial consonants, meaning they are produced by bringing the two lips together.
* Passive articulator: The passive articulator refers to the part of the mouth that the active articulator (the tongue or lips) comes into contact with. In the case of "b" and "p", the passive articulator is the upper lip.
The only difference between "b" and "p" is that "b" is voiced (vocal cords vibrate) and "p" is voiceless (vocal cords do not vibrate).