Abstract: A method monitors an ESP with a pump for pumping oil, gas, water or other fluid media, which pump is driven by an electrical motor. Acoustical phenomena of the motor and/or the pump are used as a state variable for pumping the media. The acoustic phenomena are measured as electrical signals and the electrical signals are discriminated in respect to the pumped media. In the corresponding apparatus for monitoring of ESP, with pump section(s) for pumping a mixture of oil, gas and water, which is driven by a motor section(s), whereby at least one acoustic sensor is placed near the ESP.