From the SRD
The character emits an ear-splitting yell that deafens and damages creatures in its path. Any creature within the area is deafened for 2d6 rounds and takes 2d6 points of damage. A successful save negates the deafness and reduces the damage by half. Any exposed brittle or crystalline object or crystalline creature takes 1d6 points of damage per caster level (maximum 15d6). Crystalline creatures are allowed Fortitude saves to reduce the damage by half, and creatures holding fragile objects can negate damage to them with successful Reflex saves.
A deaf character, in addition to the obvious effects, suffers a –4 penalty on initiative and a 20% chance to miscast and lose any spell with a verbal (V) component that he tries to cast.
The shout spell cannot penetrate the spell silence.
END
A creature that has no sense of sound would take damage from the spell but would not suffer any further adverse effects. Unless they are supposed to be able to hear. But in the case of a creature that simply has no sense of sound, it would only take damage and would not suffer any penalties to initiative. Though if the creature can't hear, it is quite likely it can't cast spells anyway. Unless, of course, it has a special ability to do so otherwise. Makes sense.
