Apparatus and methods for mapping vibrations in a pipeline using an in-flow vehicle (“IFV”) are provided. The IFV is propelled through a pipeline, either by fluid flow or by self-propulsion. The IFV includes one or more vibration sensors, a power source, and electronic instrumentation that is programmed to records vibrations present in the fluid periodically as the IFV travels through the pipeline. Processed vibrations are periodically stored in the memory of the vehicle and subsequently transferred to a computer. The processed vibrations are analyzed to determine the location of the vibration energies emanating from any leaks present in the pipeline.