Sonic Soul

On the surface, the sonic soul sorcerer is not dissimilar from a bard, with their manipulations of sound and magics that affect it. But in reality, their potency runs deeper: altering space to affect the propagation of energies, for both harmful and helpful effect, and harnessing the true, destructive force and speed of sound.

Dampen

Starting at level 1, you gain permanent resistance to thunder damage.

Once per long rest, when you would suffer damage from the following list, you can use your reaction to become resistant to that type of damage until the start of your next turn:

• Cold
• Fire
• Lightning
• Radiant

Sound Barrier

You harbor within yourself energetic resonance that harms melee attackers. At 1st level, the first time per round that a creature strikes you in melee, you can deal thunder damage equal to your sorcerer level to it.

Destructive/Constructive Interference

Starting at 6th level, you gain the ability to alter how energy propagates through the world. As a reaction, when a mundane or magical effect that you can see within 60 feet would deal cold, fire, lightning, thunder, or radiant damage, you can use your reaction to to create a 15-foot radius field, within which the triggering damage is halved. Alternatively, you can boost its power, adding a number of 1d4s to its damage, of the same type, equal to half your sorcerer level, rounded down. 

You can use this ability a number of times equal to your Charisma modifier, minimum 1. All uses are restored after a long rest.

At 18th level, the range of this effect is increased to any point you can see, and its radius increases to 30 feet.

Speed of Sound

You have learned to suffuse yourself with the harmonies that you affect such that it bolsters your speed. At 16th level, whenever you deal thunder damage, or you would increase or decrease the amount of thunder damage that a creature other than you suffers, your movement speed increases by 20 feet until the start of your next turn.

Reverberate

You have learned to let the magical energies reverberate within you, creating a font of near-endless power. At 18th level, whenever you cast a spell that deals thunder damage, you can regain a spell slot that is lower than the one expended. The recovered spell slot cannot exceed 5th level.