I suggest jumping off the tower and killing yourself. Seriously, it shows up in the screen that you died. There's your "shout".
If it doesn't yield results, go to orbit and come back down. Hopefully you get a new instance of the tower and can kill yourself again for notice.
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One major flaw in this plan mate. Activision Blizzard confirmed that over 4 million players logged on to Destiny during its beta phase, and as of this comment, you only have 23 replies to this thread. Lets say, hypothetically, all your replies were from individual posters. Thats only a 0.000575% response rate to your lame ass idea. The odds of running into anyone on this thread are incredibly small. So when you start throwing yourself off the tower in the vain hope that someone here happens to see you. I hope it was worth it. Stick a sign up board in the tower or a customisable emote to signal your willingness I say. It would take no time at all to implement and would be a helluva lot more effective than an idea that has people asking "is there something down there I should be looking for?" while you cry and wonder why no one is inviting you to a raid.