Airspeed

This was a winter flying day at Hyner PA. I wanted to practice stalls while monitoring airspeed, but that didn't work out. It was pretty active air (thermal bumps) so it wasn't a smooth day to try the stalls. I did hit some thermal bumps for some lift but also fell in some holes or odd pockets of air that made me uncomfortable with my clearance above the trees. In those odd pockets of air, my airspeed dropped off without me really doing anything to cause it. It was like I was going along and had the wind noise and also the impeller noise from the Ball 652 most of the time when I had good airspeed, but at times when hitting an odd pocket of air I noticed the "no wind" noise... eerily quiet sound...which can be bad and cause an unwanted stall. During those "no wind" moments the airspeed indicator did show a drop off. What I really want to do is have a calm day where I can purposely cause stalls safely, high above the terrain, and watch the airspeed indicator and note my control bar position. I want to do the same practice with both of the gliders that I regularly fly...that is the goal.