mouthpiece for HT-tube vuvuzela

I made the vuvuzela as a training device for my tone on wind instruments. The parts for this build are the mouthpiece and HT-tube with a diameter of 40mm. The length of the tube should be between 1.20m-1.50m(you can connect shorter pieces of the tube, just like me) . If it is shorter than that it is very hard to make a tone with the vuvuzela.