echoing

Echoing refers to the repetition of a sound caused by the reflection of sound waves from a surface. When a voice or noise is produced, some energy travels to a reflecting surface, returns after a delay, and is heard again as a distinct repetition or as a persistence known as reverberation. The term can also describe analogous repetition in language or memory.

Physical basis and characteristics: The time between the original and the reflected sound is t = 2d/c, where d is the distance to the reflector and c is the speed of sound in air (about 343 m/s at 20°C). Clear, discrete echoes require the surface to be sufficiently distant and the sound to have energy to travel back before subsequent reflections mask it. In small rooms, reflections merge into reverberation; in large, smooth-surfaced environments you may hear a single echo.

Natural and architectural contexts: Echoes occur in canyons, caves, and mountainous areas where surfaces reflect sound, as well as in buildings and concert halls where geometry shapes reflections. Specific phenomena include flutter echo, a rapid series of echoes between parallel surfaces, and slap echo, a distinct, sharp echo arriving shortly after the direct sound.

Biological and technological uses: Bats and dolphins use echolocation, emitting pulses and listening for returning echoes to determine distance, shape, and texture of objects. Humans employ sonar in navigation and underwater exploration; echo-sounding devices measure depth by emitting sound pulses and recording their return time.

Psychology, language, and memory: In cognition, echoing can refer to the short-term auditory memory called echoic memory, which briefly stores sounds after they occur. In social communication, echoing may describe repeating or paraphrasing another person’s words to demonstrate understanding or facilitate interaction.