Audio phenomena refer to various effects and occurrences related to sound. These can include concepts like echo, where sound reflects off surfaces and returns to the listener, and doppler effect, which describes the change in frequency of a sound wave as the source moves closer or farther away. Another interesting audio phenomenon is harmonics, which are higher frequencies that resonate alongside a fundamental tone, enriching the sound. Additionally, binaural beats occur when two slightly different frequencies are played in each ear, creating the perception of a third tone, which can influence relaxation and focus.