Here is what I have been using, especially when teaching a class and I have been very happy with it. Also proof you don't need to spend a fortune on it as these were about $60 at Dicks Sporting Goods. . . Now these are analog and not digital but they work.
They run on two AAA batteries and you can see the volume control on the right side in the lower photo. The black spot on the left is the microphone, one on both sides of the headset so you get stereo hearing like normal. They also have an input plug so if you want to you can plug in your MP3 player. Not sure I would do this at the range but it works when I am mowing the grass . . . .
For sound you can actually turn it up to help you hear things you would normally miss if out hunting or such. Now that would be bad except it also has a special circuit in there so if the sound gets to unsafe levels (such as a gunshot) it turns off the mic and you get the hearing protection. I have found they fit better than the ear protection you can get at the hardware store, seems like the better fit means less noise leakage around the glasses frames and such.
I have used these for almost six months now and have been very happy with them. They are comfortable and when am working with students on the range I can hear everything going on. I think that is key to these for a class. They add to the safety level in my book. I can hear what is going on, any range commands or comments from other instructors or the students and you can talk at a normal level yet still keep your hearing safe.
I highly recommend these to anyone doing a lot of shooting and who still wants to hear what is going on around them. Be safe out there folks and have fun!