I could add a checkbox to turn on/off automatic volume control. I'm lacking knowledge on how the volume should be adjusted. There is a loss of volume caused by the difference in the length the sound travels in the air between the speakers and the listener (If the speakers are not all at an equal distance to the listener). I need to know how much a sound signal is attenuated by a distance in air at about 20C (dB/meter or something). I know the distance so I can calculate the dB loss caused by the propagation of sound throught the air. I then need to figure out what scaling fraction to use with that dB loss. I see a problem with that approach. The sound produced by the speakers has a volume control. To reduce the volume by a specific amount of dB (what you hear, not the signal that comes out of the sound card) at two different speaker amplifications you would use two different volume scaling fractions. Not sure if this is correct. Please explain how/why the SPL sliders should be used. Maybe my thinking is incorrect. What I know is that I don't know how to do the automatic volume control with my current knowledge. I can do the programming as long as I know what I need to calculate, what are the equations,etc. Feel free to share any knowledge that can be useful. Links to webpages providing useful information are welcome.