View source for SAY AMBIENT SPEECH

{{Native
|np=5
|p1t=Handle
|p1d=Char to say the speech
|p2t=String
|p2d=The id of the speech to say
|p3t=Integer
|p3d=Always speak (0 = depend on P4, 1 = always speak)
|p4t=Integer
|p4d=Allow speech once per 15-17 seconds
|p5t=Integer
|p5d=Cancel megaphone (0 = don't cancel, 1 = cancel)
|r=0
}}

Makes the specified char say the specified phrase. If P5 is 1, speech that ends with _MEGAPHONE will be spoken without echo.

By the looks of it, if P3 and P4 are both 0, speech will never be spoken no matter what.

If P3 is 1, regardless of P4, speech will always be spoken.

If P3 is 0, and P4 is 1, speech will only be spoken if more than 15-17 seconds since the previous speech was spoken has passed. (Not sure on the exact time, or if the time is determined from the time the speech starts playing, or after it ends. However, it does seem like it's around 16.7 seconds)