Abstract: Multi-sensors passive arrays are used to detect different objects emitting wideband acoustic signal to aquatic medium. The most important design problem is to proper match the size of the antenna and number of sensors to the wideband frequency range. Especially the multi- mode operation significantly increases the detection efficiency. In case of cylindrical antennas interesting is object detection at two frequencies. The first frequency results directly from the antenna radius, whereas the second one is doubled. The article presents detection capabilities of antennas composed of several hydrophones.