Anywhere you have a joint, glued or bolted, you are going to disipate vibrational energy to the environment through that "seam" or joint". This is just a simple fact of physics, especialy because sound travels faster through a solid than it does through a liquid or gas, increasing the frequency that the vibrations will transverse the length of the guitar scale. the poster above who stated that a glue on or bolt on neck compresses better than a through neck is mistaken. that "compression" actually disrupts the vibrations through a solid top guitar. For this reason, a through neck, consisting of a single peice of wood will resonate better than a bolt on or glued on neck. I am sure dogs can hear a difference, but a human would be hard pressed to distinguish sonic differences, except perhaps in the length of sustain a guitar can achieve. the less vibrational energy you lose through seams or joints, the longer the vibrations can reverberate through the material. Many super high end, handcrafted guitars are neck through for this reason.