Apparatus and method for measuring the pressure inside a pipe or container

An apparatus and method for measuring the internal pressure of a pipe or container is disclosed. The apparatus includes an acoustical transmitter (Tx1) mounted on a wall (1) of said pipe or container and a signal generator (2) connected to said transmitter and which is adapted to provide a signal to the transmitter. The signal from the transmitter is detected by two receivers (Rx1, Rx2) mounted on said pipe or container in a distance from said transmitter (Tx1). A processing unit (3) is connected to said transmitter and receivers, the processing unit being adapted to measure the travel time of an acoustical signal propagating between two receivers in the wall (i) and determine the pressure inside the pipe or container from said travel time.