So, by the rules as written, it should be trivially easy for a mage to cast a MuIm spell to greatly enhance the volume of their voice. It's a base level 1 effect to change a single sensation of an object, such as the sound it produces. With Range: Personal and Target: Individual, that's still a level 1 spell. If you use duration: Diameter (easily long enough to get you through most of a fight, for instance, and if not then you can just cast it again) then that makes it - gasp! - a level 2 spell.
Now, I can see a few ways of bumping the level of the spell up, such as increasing the Target to Part, so it only affects the volume of your voice and not the sound of your footsteps, for instance, but that's still a trivially easy spell that vastly enhances any voice-range spell. What could a Flambeau do if the range of {ilum Of Fire or Ball Of Abysmal Flames effectively doubled, or even tripled? It seems so powerful that there must be a reason it doesn't work, or that it's harder than it seems. I just can't find one under the Rules As Written.
Out of character, the reason seems to be merely to prevent exploits like you suggest (and similar exploits).
I think that, in-character, it would be explained as a manifestation of the Limit of Essential Nature. The length of Voice Range effects is a part of the essential nature of Hermetic magic.
I doubt it is "hotly-debated", as it is pretty trivial to prove that voice enhancing magics don't increase Voice range, and there is a clear, well-known work-around. Invent a Sight Range effect, instead. Most magi would probably be happy with leaving the issue there.
Having said that there do appear to be some anomalies, as merely yelling does increase Voice Range, and magic quietening effects do reduce Voice range. So, it does seem like an obvious flaw in Hermetic Theory that interested magi would be researching (successfully or not).
Not so hotly debated - most players (on these boards, at least) accept that AM is not by default a "high fantasy" game, and so a spell that echoes across counties and kingdoms like thunder rolling across the land is not expected, and not even accepted.
grin but of course you can make a spell so that your voice does 'echo across counties and kingdoms like thunder rolling across the land'; it's just that gaining that area of effect doesn't rely on having the Range of that spell as 'voice'....not that I've actually done this yet.
'Jupiter's Shout Signifying the End of the World' CrAu L50 Ritual
This spell produces a loud thunderclap which is audible almost everywhere. See 'Jupiter's Resounding Blow', but without actually deafening anyone or being usable indoors.
Base 2 (base 3 to need a stamina roll to avoid deafness); Duration - momentary; Range - touch +1; Target - Individual (which is a boundary, for Auram, but needs lots of size modifiers...how big is eg Europe if you wanted to affect all of it? (in paradigm, something more like 'Western Christendom' would be the label rather than 'Europe') +5 size gets 40 miles diameter, Europe is approx 4,000,000 sq miles according to wikipedia, every size increase gets x10 bigger.
size 5 6 7 8 9 10
area 40 400 4,000 40,000 400,000 4,000,000
ie size +10. Lets go for +11, so all the corners are affected and not just a circular shape.
Have I added it up correctly? Legal? (Silly? of course!)
Technically this isn't your voice, it's clap of thunder. Does anyone feel like making the vocal equivalent?
Correctly ? No, sorry. Even if size +5 if a 40 miles diameter (and the spell Wrath of Whirling Wind and Water supports it, even if standard Boundary sizes would say 20 miles instead, calculating from a 100 pace Boundary (the individual for Auram) and increasing the area by a factor of 10 with each size increase), you then proceed to compare that linear distance to an area.
A 40 miles diameter area in fact covers approximatively 1250 sq miles, so you can save yourself one size, maybe two: Size 9 is 12,500,000 square miles, enough for Europe.
Legal ? Well, you seem to think there is no need for extra magnitudes for an unnatural weather phenomenon, but I would argue your thunderclap is in fact completely unnatural, both from size and from the fact it is heard over such a large area but does not deafen anyone anywhere within it...
And of course it's silly. Utterly and completely silly It would get you Marched so fast, you would be halfway to the Afterlife before the sound of it would even catch up to you
Well, if I've put too many sizes into the spell, then the overall level is OK if you think that thunderclaps are unnatural...I'd say that NOT being deafened by thunder is the 'natural' version. Base 3 specifies 'deafening thunder' as opposed to a 'normal weather phenomenon' at base 2. The unnaturalness of the size is paid for in the size adjustments already and I see no reason to have to pay for that twice (and, in modern thinking at least, there is no reason why a natural clap of thunder couldn't be heard over a massive area - volcanoes have been heard across the entire world and without the sound actually harming people directly. In paradigm, they locals would probably all think it were divine or infernal). On the other hand, something like this should be about level 50 (Rule 1 applies) in my opinion.
You could do it with CrIm. Base 1 (image affecting a single sense), +1 for complexity (spoken word), +1 touch brings us to level 3, then stack a whole lot into size. Size for CrIm translates to an increase in volume, with the base being the amount of noise a single adult human can make.
That way, rather than just having a big 'boom' noise, you can shout out "March me!"
This could well be the start of an amusing Guernicus story of tracking down the culprit, because someone somewhere will be arrogant/stupid enough to do it.
It would get you Marched so fast, you would be halfway to the Afterlife before the sound of it would even catch up to you 