I dont care how much Sound you have it doesnt have any damaging characteristics until you include the overpressure/concussive/ harmonic effects. Its not the SOUND that does damage, Its the side-effects.
Without the sound, you don't have the effects. Harmonic effects are the result of the sound vibrations being of the right frequency to set up a resonating vibration in the target. The pressure is also a direct result of the sound wave, not a "side-effect". Concussive effects are the result of violent shaking. If there's no sound, there's no vibration, no shaking, and no concussion.
Sonic is just Force damage that doesn't auto-hit incorporeal creatures.
No, force effects that don't affect incorporeal creatures or objects have no spell descriptor at all. See
unseen servant, which creates an "invisible, mindless, shapeless force" but has no force descriptor and no ability to move ethereal objects. See also
telekinesis. There's also the fact that there is no "force resistance" special quality and there is no
endure elements (force). Sonic damage and force damage don't have anything to do with each other.
A Sonic Fireball is a Silent Blast of Concussive Force is just as viable as a Cacophonous Roar.
No. That is something that you made up. The feat says that you can modify a spell with an energy designator to use the chosen type of energy instead. For Energy Substitution (sonic), that means that the spell uses sonic energy. See the definition of "sonic" again, and read it until you understand it.
A +1 Screaming Sword is a Star Wars Vibro-blade. Sonic doesnt have to make noise.
Maybe not noise that humans can hear, due to it being outside their range of hearing. That doesn't mean it isn't stopped by
silence.
Silence negates the blindsight quality of bats and other creatures that use ultrasonic sound for echolocation. As for a vibroblade, that's a completely seperate issue; the vibration of the metal aids the metal's cutting effect. Anyway, we're discussing what
silence does in D&D. I don't play Star Wars and I don't care how they handle sonic damage or any other type of damage there.
Actually, Cold is the most powerful substitution. There are quite a few Fire Subtypes that take double damage from Cold and fewer resistant than vice-versa. Sonic just has (nearly) no-one resistant, but also no-one vulnerable. Except Crystal creatures, which is what? 2? 3?
The Order of Preference is
1 Cold
2 Fire-Sonic
4 Acid-At Least it stops some regens
5 Electricity- Lots of Resistance, Only the Iron Golem is sort-of vulnerable
Cold damage is completely useless against cold creatures. And there's no need to take a feat to get cold spells (or fire spells, for that matter) with so many efficiently damaging spells of that type already existing. As a substitution (which is what you were arguing), cold (and fire) don't make sense unless you need to qualify for a PrC or want a themed character at the expense of power.
Sonic damage, OTOH, without a feat isn't efficient at all (2d6 for
shout, a 4th-level spell? No damage at all for
shatter except against crystalline creatures?); the upside is that almost nothing has any protection against it. Sonic substitution gives you both great penetrating power and efficiency, which is why it is the best substitution.
At the point of casting Shatter makes a sound, but you dont have to hear the noise to be affected by it. Unless the caster is in the Silence effect the spell goes thru.
You don't have to hear the noise, but the noise has to strike the target, and
silence prevents the noise from entering. The wording of the
shatter spell says flat-out that it is the
noise that has the effect. Unless you can find some errata that changes what
shatter actually says, I'm not going to argue this point any further because the plain wording of the spell makes it obvious that you are simply wrong.
Only Shout is affected by Silence, and Yes "the designers did always feel the need to spell everything out in simple terms." If the book doesnt say it, it isnt the Rule. That been the general rule of 3e.
If I pour water on a campfire, does it not extinguish it because the designer never said, "Rule 1 of campfires: pouring water on them will put them out?" If I leave a glass of water in the sun, will it never evaporate because the designers never made a rule about evaporation? Of course not. The players are expected to use logic and common sense in interpreting the rules. And it's a logical, common sense interpretation of the rules that
silence blocks sonic damage.