Head-related transfer functions (HRTFs) are mathematical models that describe how sound waves interact with the human head and ears. They help determine how we perceive the direction and distance of sounds in our environment. HRTFs take into account the shape of the head, the ears, and the torso, which all affect how sound reaches each ear. By analyzing these interactions, HRTFs can be used in audio technology to create realistic 3D sound experiences. This is particularly useful in virtual reality, gaming, and hearing aids, where accurate sound localization enhances immersion and communication.