When you place a mob spawner there is no sound. But when breaking one there is sound.

I was using an ocelot spawner. Happens with every other spawner though.

Reproduction of Bug:
1. Get a mobspawner. (/give <playername> 52 1)
2. Place it.
3. Listen to it.
4. Delete it.

Oh, and I also have the sound for placing a mobspawner. (that "click-ish" noise. That one where you place down an ore block. I have that noise. It won't play with mobspawners though, so don't ask me if I have the sound. I do.)