Testing iPhone microphones

Hello. I have an iPhone 6+ and it has a broken microphone(s). The Main mic at the bottom was replaced, but there's still issues with Siri, audio in videos captured with both front facing and rear facing cameras and speakerphone. In these cases, there's no audio. Voice memos and talking without speakerphone mode on is fine. How can I test whenever the receiver mic or the rear one is broken?