I’m not certain if there are any lower animals that possess sensory organs similar to ears and have more than one or two of them. However, in mammals, including humans, the number of ears is limited to two. The reason behind this can be attributed to the concept of triangulation, which requires two ears placed as far apart as possible, typically on opposite sides of the head. Symmetry also appears to have played a significant role in evolution, as evident in the presence of two arms, legs, eyes, and so on. Adding more ears would not provide an evolutionary advantage, whereas having two ears clearly improves hearing capabilities. Hence, evolution seemed to have halted at the development of two ears.