On Fri, Jan 3, 2014 at 4:03 PM, Charles Z Henry <czhenry@gmail.com> wrote:

Why do we see this technique applied with high frequencies?  At the node locations, there is the highest peak spatial derivative of the pressure while at the same time, the volume velocity of air goes to 0.

Vice-versa at the anti-nodes.

I got that wrong: 
The peak pressure difference occurs where the volume velocity is zero. 
The location of the peak spatial derivative of pressure coincides with the location of peak volume velocity.