There is provided a method of estimating flowrate in a pipeline based on acoustic behaviour of the pipe. First acoustic data is measured from the pipeline. A flowrate of the fluid in the pipeline is then estimated. The estimation is based on the first acoustic data and based on a correlation established between second acoustic data and corresponding flowrate data from an experimental pipeline. The correlation is established by a machine learning process (which may include the use of an artificial neural network, such as an autoencoder). The second acoustic data and corresponding flowrate data are used as inputs to the machine learning process.