Wiktionary
n. An early sign or indication of something; a foreshadowing.
Wikipedia
Pre-echo, sometimes called a forward echo, (not to be confused with reverse echo) is a digital audio compression artifact where a sound is heard before it occurs (hence the name). It is most noticeable in impulsive sounds from percussion instruments such as castanets or cymbals.
It occurs in transform-based audio compression algorithms – typically based on the modified discrete cosine transform (MDCT) – such as MP3, MPEG-4 AAC, and Vorbis, and is due to quantization noise being spread over the entire transform-window of the codec.
Usage examples of "pre-echo".
Scanning lasers in the comm unit traced a blue-lined image shadow on the windscreen: an electronic pre-echo of the larger-than-life holo-image projected into the burning night outside.
It was a soft voice, not ten feet away from him, and it wasn't laughing this time, as he had heard it in those ghostly warning pre-echoes that his powers had provided for him on the street.
The noises of the ship-the creak of the rigging, the uncertainty of the sails whenever the wind shifted, the protest of the waves as the dromond shouldered through them-sounded like pre-echoes of anger or grief.