[linux-audio-user] seeking simple library to detect sound volume

Hello, I've been looking on the web, and have visited the excellent resource linux-sound.org, and am a bit overwhelmed as there are so many choices, most much more elaborate than I need. What I need is the ability to monitor sound going from the computer out to my sound card, and to report when the volume exceeds a certain threshold. I need no graphic capability and as I will be writing my own application around this I prefer as simple and straightforward a library as possible. In fact I don't even need a library - a C function would be ideal! Extra features that would be nice, but not critical, would be the ability to have one or more filters so that I could report on the volume in various frequency ranges. Do any of you have any suggestions for me? Thanks, Michael