After being selected "correct answer", I encouraged OP to continue asking... this answer is complete except one crucial aspect. OP wants to know if timeline could look like this:
- T4 Audience boos again
- T5 John begins to speak
Anwer is "no" but he/she needs to know why. Exmple:
- "John begun speaking when the clock struck noon."
- "Scarcely had John begun speaking when the clock struck noon."
I'm too tired to dig into tense/aspect/etc right now. Anyone is free to help me out on this / make suggested edit or comment. I've got to sleep and will review in a day.
Scarcely had John begun speaking when he was again booed by the audience.
- T1: ???
- T2: audience boos John (deduced from "T5:again" below)
- T3: ???
- T4: John begins to speak
- T5: audience boos again
SEMANTICS: Statement at T5 indicates that the audience booed John at least once before, such as at T1, T2, or T3. I will put it at "T2" to indicate the prior booing.
LOGICAL ANALYSIS: The statement makes no inference that John had spoken once before. There are all kinds of possibilities (non of which are really "important"):
- Maybe they booed him for some other reason, like he was on a talent show and road onto the stage with a unicycle honking a horn, juggling some plates that dropped and broke - and maybe they booed him for that.
- Maybe he spoke before, and they booed him for that.
- Maybe they booed him as he walked on stage because he was a known speaker unfriendly to the audience's cause.
- Maybe the audience was given a sign to boo him, as a prank.
CONCLUSION: The only thing known is marked in the timeline.