The noise of metallized film capacitors is caused by the vibration of thin film in AC electric field and how to eliminate it is still a technical problem in the present capacitor industry. The mechanism of the reason of noise generation and the "bubble noise" between noise and temperature are revealed through anatomy of the noisy product and analysis of noise feature

affirming that the bubble between the film layers due to high temperature of the heat setting process is the root cause of the noise. The noise strength and occurrence probability can be improved by material selection and process modification. However

it is very difficult to eliminate the noise by only thermal setting process.