The invention concerns a method for investigating a scattering medium, especially a biological matrix, with intensity-modulated light. In order, in such a frequency-domain measuring procedure, to reduce the expenditure on electronics without restricting accuracy of measurement, a method is proposed, in which, in order to investigate a scattering medium, especially a biological matrix, with intensity-modulated light, a high-frequency modulation signal is generated by a frequency generator (18), the intensity of a light emitter (10) is modulated with a modulation signal and the light from the light emitter (10) is radiated into the medium, the modulation signal includes frequency chirps during which the modulation frequency is tuned from an initial frequency to a final frequency, the modulation signal is delivered from the frequency generator (18) via at least two different signal paths (23A, 24) to a signal mixer (31), so that during a frequency chirp the input signals of the signal mixer (31) differ by a differential frequency whose magnitude is a function of the difference between the signal transit times over the at least two signal paths (23A, 24) and of the rate of change of the modulation frequency, wherein at least one of the signal paths includes a light path section (20A) passing through the medium as a measurement signal path (23A), and the output signal of the signal mixer (31) is further processed to produce information relating to the scattering medium (FIG. 2).