Hearing aid, comprising: an acoustoelectric transducer for converting an acoustic signal into a first electrical signal; a pickup device for picking up an electrical or electromagnetic signal and converting the electrical or electromagnetic signal into a second electrical signal; a signal estimation device connected in signal communication with said acoustoelectric transducer and said pickup device; a signal processing device connected in signal communication with said acoustoelectric transducer, with said pickup device and with said signal estimation device, said signal processing device being configured to receive the first electrical signal and the second electrical signal and to process the first and second electrical signals into a third electrical signal; an electromechanical transducer connected in signal communication with said signal processing device and configured to convert the third electrical signal into an acoustic signal and to output the acoustic signal; wherein said signal estimation device is configured to determine a correlation between the first electrical signal and the second electrical signal in a first predetermined frequency range of a plurality of separate or partially overlapping frequency ranges and to communicate the correlation to said signal processing device, wherein said signal processing device is configured to adjust a proportion of the first electrical signal and of the second electrical signal in the third electrical signal in a predetermined second frequency range of the plurality of separate or partially overlapping frequency ranges depending on the correlation; and wherein the first and second frequency ranges are completely different or only partially overlapping, wherein said signal processing device is configured to reduce the proportion of the second electrical signal in the third electrical signal as the correlation increases. an acoustoelectric transducer for converting an acoustic signal into a first electrical signal; a pickup device for picking up an electrical or electromagnetic signal and converting the electrical or electromagnetic signal into a second electrical signal; a signal estimation device connected in signal communication with said acoustoelectric transducer and said pickup device; a signal processing device connected in signal communication with said acoustoelectric transducer, with said pickup device and with said signal estimation device, said signal processing device being configured to receive the first electrical signal and the second electrical signal and to process the first and second electrical signals into a third electrical signal; an electromechanical transducer connected in signal communication with said signal processing device and configured to convert the third electrical signal into an acoustic signal and to output the acoustic signal; wherein said signal estimation device is configured to determine a correlation between the first electrical signal and the second electrical signal in a first predetermined frequency range of a plurality of separate or partially overlapping frequency ranges and to communicate the correlation to said signal processing device, wherein said signal processing device is configured to adjust a proportion of the first electrical signal and of the second electrical signal in the third electrical signal in a predetermined second frequency range of the plurality of separate or partially overlapping frequency ranges depending on the correlation; and wherein the first and second frequency ranges are completely different or only partially overlapping, wherein said signal processing device is configured to reduce the proportion of the second electrical signal in the third electrical signal as the correlation increases.