What best describes a term for sound waves that reflect off surfaces, creating recognizably delayed sounds?

The term best describing sound waves that reflect off surfaces and create recognizably delayed sounds is echoes. When a sound wave encounters a surface, it can bounce back, or reflect, resulting in an echo when the time delay between the original sound and its reflection is noticeable to the human ear. This phenomenon occurs in environments like canyons or large halls, where sound waves travel along a longer path before returning.

While reverberation is related and can describe the persistence of sound in an enclosed space due to multiple reflections, it refers more to the continuous sound that continues to be heard rather than a distinct repeat of the sound that is easily recognized as separate from the original. Harmonics involve the multiples of a fundamental frequency that contribute to timbre but do not deal with reflections and delays. Noise cancellation refers to techniques used to reduce unwanted sound rather than phenomena related to echoes or reflections. Therefore, echoes specifically capture the essence of the delayed sounds created by reflected sound waves.