Abstract: A procedure for analyzing air content of a liquid, e.g. pulp slurry, wherein the ratio I.sub.att /I.sub.sc between ultrasound attenuation and scattered ultrasound attenuation and/or the logarithm log (I.sub.att /I.sub.sc) is determined. The respective measuring apparatus comprises an ultrasound transmitter (1) and an ultrasound receiver (2) and a scattered ultrasound receiver (3), the latter being disposed to measure members (4) for determining the ratio I.sub.att /I.sub.sc and/or the logarithm log (I.sub.att /I.sub.sc).