An echo is our own perception of a returning wave. Listening to it is hearing our own hearing happening somewhere, somewhen.
Listening is a totally different process than recording a sound. If we use a mechanical device to record a wave and its echo (to separate ourselves from the observer’s point of view), we capture a pattern of the wave — an image. But there is no way to truly experience a sound or an echo without experiencing it in time. We may look at spectrograms, but it is the temporal unfolding that makes listening such a delicate tool for observing — lose your focus for a second, and you might miss it…
Perhaps it is due to the speed of light and the biological structure of our eye that we tend to associate seeing with what happens right now. But from studying visual illusions, we also know that our mind is easily fooled. We might see movement in a still image or make wrong assumptions about the dimensions of the world. But the visual world does not echo in the same way as the sonorous world.
Jean-Luc Nancy remarks in Listening: “Whereas visible or tactile presence occurs in a motionless ‘at the same time,’ sonorous presence is an essentially mobile ‘at the same time…’”
For Nancy, listening is observing the internal resonance of a sound within us. To experience listening, we have to co-exist with the sound for its whole duration. A text or an image doesn’t impose a fixed timeline for our perception, although it may hint at one. But a sound, with its echoes, always has a strong temporal correlation. You can’t change the timing (tempo) of the sound without changing its properties; a sound is not as translatable as theoretical concepts — it is much more delicate than that.