A method for determining a height (hs) of a settled bed in a mixture in a loading space (1). The mixture consists of a settled bed (5) and a mixture soup (3) which is located above the settled bed (5). The method includes: a) providing an elongated resonance member (10) in the loading space (1) which extends in a substantial vertical direction, b) measuring a resonance frequency (fo) of the resonance member (10), c) computing a height (hs) of the settled bed (5), Action b) includes determining an indication of or imposing the tensile force (Fs) acting in the longitudinal direction of the resonance member (10) and c) includes computing a height (hs) of the settled bed (5) based on the measured resonance frequency (fo) and the determined indication of the tensile force or the imposed tensile force.