Chirp profile through a barrage consisting of a series of lines of poles probably representing repair phases, from the Late Viking Age/Early Middle Ages. The barrage consists of lines of poles that have disintegrated above the sea floor. The barrage also includes a number of poles which probably do not form a straight line; the acoustic signal for the poles therefore varies. The sailing line was perpendicular to the barrage and reveals its various repair phases. Recorded by Grøn.