The speed of sound in plastic at 25 degrees Celsius depends on the type of plastic. Here are the speeds of sound for some common plastics at 25 degrees Celsius:

- Polyethylene (PE): 1,950 m/s (6,400 ft/s)

- Polypropylene (PP): 2,050 m/s (6,730 ft/s)

- Polyvinyl chloride (PVC): 2,250 m/s (7,380 ft/s)

- Polycarbonate (PC): 2,450 m/s (8,040 ft/s)

- Polyethylene terephthalate (PET): 2,550 m/s (8,370 ft/s)

- Polystyrene (PS): 2,650 m/s (8,690 ft/s)