Speaking virtually is an ACTIVE-ity. Sit up. Get grounded. Go.
Many of us are spending hours and hours in online meetings every day. The bandwidth issues, the slight delay in signal, the heads in floating boxes...all that stuff makes it difficult to stay engaged as a listener. Throw flat, inactive speaking into the mix and you have a recipe for utter boredom and disconnection. You want to be treated better as a listener? Do unto others as you would have others do unto you.
Assume a posture in your chair that has you ready to tilt forward. Put the weight of your upper body over the points where your pelvis meets the seat of the chair. It's fine to scoot back so that your lower back is supported by the back of the chair, but find your balance and keep your core muscles engaged.
Put your feet flat on the floor. Feel gravity pull you and hold you in the seat of the chair. Free your hands from your desk, resting them on your lap or on the arms of the chair (you may need to scoot your chair back a little to do so).
It is our natural design to speak with voice, face and hands; subdue the hands and the voice and face are bound to flatten out. Employ your hands when you speak online. And tilt/roll slightly forward as you speak. Think transfer. You are transferring your sound and light forward and through to your listeners.