Acoustic imaging in the ocean using ambinet noise

A method of detecting underwater objects and/or surfaces using ambient ocean noise comprising:

• directing at least one detection beam toward the object or surface to be detected and detecting reflected ambient noise from a region on said object or surface covered by said detection beam;
• detecting surrounding ambient noise outside of said region;
• comparing said surrounding ambient noise and said reflected noise to generate a contrast signal comprising frequency and amplitude information;
• and
• generating an image from said frequency and amplitude information corresponding to a shape of said object or surface.

A method of acoustic imaging and passive ranging of an underwater target in an ocean environment using ambient noise, the method which comprises:

• forming a plurality of acoustic detection beams each having a means for varying its focal distance and a region of intersection on said underwater target;
• directing each said acoustic detection beam toward said underwater target;
• detecting ambient noise reflected from each said region of intersection and generating an electrical signal therefrom, said electrical signal containing amplitude and frequency information;
• generating a multi-pixel acoustic image by combining and contrasting said electrical signal from each of a plurality of regions of intersection on and surrounding said underwater target, each pixel of said multi-pixel acoustic image corresponding to one said region of intersection;
• and
• determining an actual distance to said underwater target by varying said focal distance to obtain optimal contrast and amplitude within said multi-pixel acoustic image.