This document discusses several fundamental acoustic parameters and principles: - The inverse square law formula for sound level drop off with distance in an ideal free field environment. - Definitions of reflection, absorption, and transmission coefficients that describe how sound interacts with surfaces. - The relationship between reflection, absorption, transmission coefficients and reverberation time (RT60). - Examples of how acoustic treatment can alter the reflection and absorption coefficients in a room to control its RT60 and reduce resonant modes. - Explanations of normal mode resonance and how room dimensions relate to resonant frequencies. - Strategies for acoustic treatment of existing rooms to reduce resonance and achieve a target RT60.