Abstract: The disclosure relates to methods and apparatus for identifying rheological properties of liquids from acoustic signals generated by liquid flow through a pipe. Example embodiments include a method of identifying a rheological property of a liquid flowing in a pipe (101), the method comprising: detecting an acoustic signal generated by the liquid flowing in the pipe using a sensor (105) attached to a rod (104) extending from a wall of the pipe (101) into the liquid; sampling the acoustic signal to provide a sampled acoustic signal; transforming the sampled acoustic signal to generate a sampled frequency spectrum; correlating the sampled frequency spectrum with a stored frequency spectrum from a database of stored frequency spectra of liquids having predetermined rheological properties; and identifying a rheological property of the liquid based on the stored frequency spectrum.