The understanding of speech is to be improved in cases of hearing loss in which certain frequency ranges can no longer be perceived even at high volume or amplification, as applicable. A frequency transposition is performed on an input signal coming into a hearing aid and specific features of an electrical input signal are detected and a transposed signal is filtered as a function of the specific features detected in the electrical input signal. The hearing aid provides appropriate facilities for detecting specific features of the electrical input signal and filtering facilities for filtering the transposed signal. The objective of this is to detect particular properties of the input signal, in particular signal properties which are characteristic of fricatives, which may possibly be lost as a result of the frequency transposition, and at least partially to restore them in the transposed signal.