Grumpy screamy stone people.
To be honest, the gulgar feels kind of underwhelming to me. It's got 10 monstrous humanoid RHD, and is Large, but its stats are underwhelming. Physicals of 20/7/17 are only slightly stronger than an ogre's 20/8/15, and the latter has significantly fewer RHD.
The +8 natural armor and free 2d6 gore are of course welcome, especially when the latter counts as Adamantine for the purpose of overcoming DR. The gulgar also has two slams, but they're weak and prevent weapon use so they might as well not exist. DR 10/adamantine is similarly quite useful.
Sonic Pulse, their supposed signature ability, is weak. A small AoE that deals 3d6 sonic damage isn't worth spending your turn on, even with the deafness rider.
Subsonic Speech is... interesting. It's a form of communication that travels quite far, is hard for foes to pick up, and is frankly quite flavorful. The issue: gulgars are completely incapable of speaking on frequencies audible by humans, making this their sole mode of communication. This means that anything trying to understand a gulgar must either learn some barely-used language and be great at reading lips, or have hearing-based tremorsense, blindsight, or blindsense.
The remaining abilities are Stability, -4 Spot, +4 Listen, immunity to sonic damage, tremorsense (duh), and free Powerful Charge.
Is the gulgar an ECL 10 character? I personally doubt it. In the end it's a melee brute with a disappointing chassis, an inability to communicate normally, and somewhat decent DR and natural armor. -0 LA.