A system for recycling planar objects (102, 102a-e) having a first major surface and an opposing, second major surface, the planar objects (102, 102a-e) comprising compressed mineral fiber material, the system comprising: a conveyor arranged to sequentially covey the planar objects (102, 102a-e) one by one through a number of stations (110, 110x, 112, 112x, 114, 116) along a conveyor direction, the number of stations (110, 110x, 112, 112x, 114, 116) at least comprising: a thickness measurement station (110, 110x) arranged to determine a property related to thickness and associated to each of the planar objects (102, 102a-e) being conveyed through the thickness measurement station (110, 110x), a sound measurement station (112, 112x) arranged to determine a property related to sound absorption and associated to each of the planar objects (102, 102a-e) being conveyed through the sound measurement station (112, 112x), the sound measurement station (112, 112x) comprising, a sound reflecting surface arranged to back the first major surface of each planar object (102, 102a-e) being conveyed through the sound measurement station (112, 112x), a sound emitter arranged to emit sound towards the sound reflecting surface, a sound receiver arranged to receive sound reflected from the sound reflecting surface, and a converter arranged to determine the property related to sound absorption based on the emitted sound and the reflected sound, and a sorting station arranged to sort the planar objects (102, 102a-e) based on their respective determined properties in to a plurality of fractions (116a-d, 116w). a thickness measurement station (110, 110x) arranged to determine a property related to thickness and associated to each of the planar objects (102, 102a-e) being conveyed through the thickness measurement station (110, 110x), a sound measurement station (112, 112x) arranged to determine a property related to sound absorption and associated to each of the planar objects (102, 102a-e) being conveyed through the sound measurement station (112, 112x), the sound measurement station (112, 112x) comprising, a sound reflecting surface arranged to back the first major surface of each planar object (102, 102a-e) being conveyed through the sound measurement station (112, 112x), a sound emitter arranged to emit sound towards the sound reflecting surface, a sound receiver arranged to receive sound reflected from the sound reflecting surface, and a converter arranged to determine the property related to sound absorption based on the emitted sound and the reflected sound, and a sound reflecting surface arranged to back the first major surface of each planar object (102, 102a-e) being conveyed through the sound measurement station (112, 112x), a sound emitter arranged to emit sound towards the sound reflecting surface, a sound receiver arranged to receive sound reflected from the sound reflecting surface, and a converter arranged to determine the property related to sound absorption based on the emitted sound and the reflected sound, and a sorting station arranged to sort the planar objects (102, 102a-e) based on their respective determined properties in to a plurality of fractions (116a-d, 116w).