When we tested the quadcopter we found it produced a lot of ultrasound interference. This time we tested our new plane (Bix-3, Hobby King) to see how it compared. We had three different propellers to test, and we also tried out some acoustic foam to try and dampened the noise from the engine.
In the graph you can see each of the propellors types across the top and the results with and without foam along the side. The three lines in each panel show three distances from the nose of the plane, 0cm, 50cm, and 100cm, the top line being the closest (0cm).
You can clearly see that across the three propeller types the foam makes a big difference to the volume of interference (note that y-axis has a log scale). All the top panels (with foam) have a lower amount of interference than the paired bottom panels (without foam). When we compare across the propeller types the Bix3 clearly outperforms the others, and the volume levels at 50cm with foam is similar to that at 300cm with the quadcopter, a great improvement.