Neither the "G" and "J" are silent... It's "Gjal-lar-horn". I think you don't even have anything remotely close in the english language to this, so it's hard to come up with an example... Imagine the sound "Yah!" (like "hah!", but with a y-sound like in "yes") and put a "G" before it. Begin speaking out the G, and follow with the Yah immediately: "Gyah!".