Question on E-caller volume?

Hello all, this is my first post here, you all have a very nice forum with a lot of useful information and I enjoy it greatly.

I have decided to try predator hunting here in northern Michigan, mostly coyotes. And I have been reading a lot of the posts on equipment and
techniques. I have ordered a .223 that hopefully will be in this afternoon. Also I have been reading a lot of the reviews on the different models of E-Callers, with the holidays around the corner and two little ones I am going to have to wait till after the first of the year to pick up one of those. So, I bought some tapes (rabbit, coyote/rabbit and woodpecker) and for now rigged up my old boom box for an E-Caller.

The question I have is on volume, since I have never hunted with a caller before, I was wondering how loud it should be. Or I guess a better question would be, when using a regular E-caller at what distance should a person be able hear it.

I ran a test with it and at half volume I could hear the rabbit distress clearly at 100 yards, now I figure a coyote can hear better than me so he should be able to hear it even farther. And after 5 or 10 minutes I could increase the volume to get the sound out farther. Does this sound like it should work?

Thanks in advance for your help,
Bill (MI)