An apparatus is disclosed, comprising a speaker suitable to be applied at a user's ear and enabled to be supplied with an audio signal for rendering; a microphone arranged in vicinity of the speaker to acquire a sound signal from sounds present in the ear of the user; and a signal processor, wherein the signal processor is arranged to subtract the audio signal from the sound signal to provide a physiological sound signal, and the signal processor is further arranged to detect a physiological measurement from the physiological sound signal. A method and a computer program are also disclosed.