Lucent researchers replaced it with an electret microphone, which picks up sound using a polymer foil more than 1, 000 times smaller than the diaphragm in a dynamic microphone that picks up fewer vibrations.
Otherwise several devices of a Heath Robinson nature are suggested boards to deflect the trajectory of urine and droppings, flashing lights, ultra-sound, unpleasant smells, stuffed owls, rustling aluminium foil and helium-filled balloons.