A method is disclosed for measuring pressure under a flexible cover by utilizing electromagnetic waves. Laser radiation is directed to the cover from a distance to generate vibration or a mechanical wave at the cover at at least one generation location of the cover on the basis of photoacoustic phenomena. Based on the electromagnetic waves, cover vibrations are detected due to the mechanical wave, and recorded to detect the mechanical wave at at least one recording location and to form mechanical wave information. Pressure information of pressure under the flexible cover is detected based on at least one recorded signal.