How do you get the default volume of the xbox?

Thanks,
Ivan

Why do you need it?

So that I set my sound effects accordingly

There is no default volume on the Xbox. Each title sets its own volume to balance its sound design against expectations. You should compare your game with the loudness of the startup sound to get a good reference. Users control the volume of their Xbox through their TV, or through their stereo -- there's no "volume control" on the Xbox although some games implement their own custom volume controls.

I fired up a few games and tried to match their volume. While you do want to blow the user out of their seats, you don't want to do it with volume.

You probably want the volume to be reasonably loud, without going too loud and ending up with digital clipping, which will sound like nasty distortion. Trying to match the volume level of commercial games is a fine start. Once you get in that ballpark, try and make a test case where your game is at it's max loudness (i.e. if the loudest point is when lots of weapons fx or some such are all going off at once) and make sure the sound seems nice and 'clean' to your ears when that level of sound is happening. The general idea in getting good audio quality is having the very loudest point be just a small bit under the maximum possible without introducing ANY distortion/clipping.

The official recommendation given to commercial game developers is they should match their sounds to the volume of the Xbox startup sound. Adjust your TV volume so that the Xbox startup is loud but not painfully so, then adjust your game sounds to make them also loud but not painfully so with this same volume setting.

You can assume most gamers will have their TV set so that other games come out ok (and if not, they can use the startup sound itself as a guide to adjust their volume while powering on the Xbox), so the goal is that with the volume set right for these other sounds, your game shouldn't deafen them when it starts up, but also shouldn't be so quiet they can't hear it.

It's also handy to open up the guide while in your game and do some simple navigation.  The guide sounds aren't all that loud, but it's a reference.

The general idea in getting good audio quality is having the very loudest point be just a small bit under the maximum possible

Actually, if your digital mixer saturates rather than wraps (or, even better, you have a brickwall shaper/limiter) then the goal is to make the very loudest point be a small bit *over* the maximum possible :-)