3D sound localization

3D sound localization refers to an acoustic technology that is used to locate the source of a sound in a three-dimensional space. The source location is usually determined by the direction of the incoming sound waves (horizontal and vertical angles) and the distance between the source and sensors. It involves the structure arrangement design of the sensors and signal processing techniques.
Most mammals (including humans) use binaural hearing to localize sound, by comparing the information received from each ear in a complex process that involves a significant amount of synthesis. It is difficult to localize using monaural hearing, especially in 3D space.
Technology.
Sound localization technology is used in some audio and acoustics fields, such as hearing aids, surveillance and navigation. Existing real-time passive sound localization systems are mainly based on the time-difference-of-arrival (TDOA) approach, limiting sound localization to two-dimensional space, and are not practical in noisy conditions.
Applications.
Applications of sound source localization include sound source separation, sound source tracking, and speech enhancement. Sonar uses sound source localization techniques to identify the location of a target. 3D sound localization is also used for effective human-robot interaction. With the increasing demand for robotic hearing, some applications of 3D sound localization such as human-machine interface, handicapped aid, and military applications, are being explored.
Cues for sound localization.
Localization cues are features that help localize sound. Cues for sound localization include binaural and monoaural cues.
How does one localize sound?
The first clue our hearing uses is interaural time difference. Sound from a source directly in front of or behind us will arrive simultaneously at both ears. If the source moves to the left or right, our ears pick up the sound from the same source arriving at both ears - but with a certain delay. Another way of saying it could be, that the two ears pick up different phases of the same signal.
Methods.
There are many different methods of 3D sound localization. For instance:
Steered Beamformer Approach.
This approach utilizes eight microphones combined with a steered beamformer enhanced by the Reliability Weighted Phase Transform (RWPHAT). The final results are filtered through a particle filter that tracks sources and prevents false directions.
The motivation of using this method is that based on previous research. This method is used for multiple sound source tracking and localizing despite soundtracking and localization only apply for a single sound source.
Beamformer-based Sound Localization.
To maximize the output energy of a delay-and-sum beamformer in order to find the maximum value of the output of a beamformer steered in all possible directions. 
Using the Reliability Weighted Phase Transform (RWPHAT) method, 
The output energy of M-microphone delay-and-sum beamformer is