Comparison of air‐gun clusters

Measurements of signatures from a variety of airgun cluster configurations have been carried out. The configurations include symmetrical two-gun clusters of Bolt 1500 C airguns, Bolt 1500 C airguns with waveshapekit, symmetrical two gun clusters of Bolt 600 C mounted parallel above each other, asymmetrical two-gun clusters of Bolt 600 C and Sleeve airgun clusters with more than two guns mounted in an in-line configuration. These measurements have been analyzed together with previous measurements reported by Vaage, Strandenes & Zaalberg-Metselaar 1990 [ 11, and give the basis for the following conclusions: regardless of source and gun type i) the optiial gun separation in a symmetrical two-gun cluster is 2.4 times the equilibrium radius of the individual air volumes ii) the improvement in primary/bubble peak amplitude ratio is on the average 2.4 times the ratio for two non interacting guns iii) the loss in peak amplitude at the optimal separation distance is 15% and iv) the corresponding bubble period is increased by 20%. The use of waveshapers reduce the relative improvement in primarylbubble peak amplitude ratio to about 1.5, and the optimal separation distance is close to 2.4 times the air volume above the waveshapers. Asymmetrical two-gun clusters are less effective than symmeuical clusters and give a relative improvement in primary/bubble peak amplitude ratio between 0.9 and 1.6, depending of the airgun volumes involved. The optimal separation distance is close to 2.4 times the equilibrium radius of the average air volume in the cluster. Increasing the number of guns in a symmetrical cluster decreases the optimal separation distance compared to the two-gun case and leads to a substantial reduction in acoustic efficiency as the number of guns increase.