If you are looking for the IPA (International Phonetic Association) "voiced bilabial fricative" in Unicode, you may not find it. Not all of the IPA characters are in the IPA Extensions block. If the character is somewhere else, not all of them have their IPA description in the annotation of the character. The voiced bilabial fricative is not in the IPA Extensions block and unfortunately the recommended character does not have an IPA annotation.
At the current time, the IPA gives the encoding for the voiced bilabial fricative as U+03B2 GREEK SMALL LETTER BETA. This character is in the Greek block, and its documentation does not make explicit that it is supposed to be used for a bilabial fricative nor that it is part of the IPA. Recently U+A7B5 LATIN SMALL LETTER BETA was encoded in the Latin script block. The IPA is not currently recommending U+A7B5 for IPA use.
The bigger question, of course, is a need to know all the characters sanctioned as part of the IPA and what their Unicode codepoints are. This page IPA Symbol Equivalents gives you that information.