Localization of noise sources is important when assessing the possible threats for a naval platform. Traditional beam forming focuses on finding and tracking the bearings to noise radiators. In this report a method for estimating the curvature of the soundfield, rendering passive ranging possible, is used. Data from a field experiment carried out at FOI´s research site at Djupviken were used in order to test the localization method. In the experiment a speaker emitted broadband noise from different positions, up to one kilometer from the hydrophone array. The array consisted of 22 sensors, with an aperture of around 20 meters. The analysis of the field experiment shows that passive ranging is a difficult task for a sonar. The range estimates are quite rough. At the distance of one kilometer the error is a couple of hundreds of meters.