They are called antinode . Midway between these positions the displacement is zero. These positions are called nodes . The energy of a sound wave is directly proportional to both the square of its frequency and amplitude. The rate at which energy is radiated or received per second is called power .
Sound intensity is the energy radiated or received per unit area.
Sound intensity decreases with distance from a sound source according to the square of the distance. This is called the inverse square law . Resonance occurs when a large amplitude of vibration is cause in a vibrating system by small periodic stimuli at the same frequency. Energy is transfered from one system to another. Resonance amplifies very sound sources.