If there is noise in the mobile phone call, you can choose a good mobile phone to try. If the noise disappears, there is something wrong with the mobile phone. If the noise still exists, it is estimated that the fault appears on the line. You can disconnect the indoor line and connect the telephone directly into the line. If the noise disappears, there is something wrong with the indoor wiring. Check indoor telephone lines, plugs and junction boxes for peeling, rust and looseness, and replace them. If there is still noise, it is a line problem, notify the relevant maintenance personnel to deal with it.