In physics and analog electronics, noise is a mostly unwanted random addition to a signal; it is called noise as a generalisation of the acoustic noise (\"static\") heard when listening to a weak radio transmission with significant electrical noise. Signal noise is heard as acoustic noise if the signal is converted into sound (e.g., played through a loudspeaker); it manifests as \"snow\" on a television or video image. High noise levels can block, distort, change or interfere with the meaning of a message in human, animal and electronic communication.