With too low a bit rate, <answer>compress</answer>ion artifacts (i.e., sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to <answer>compress</answer> because of its randomness and sharp attacks. When this type of audio is <answer>compress</answer>ed, artifacts such as ringing or pre-echo are usually heard. A sample of applause <answer>compress</answer>ed with a relatively low bit rate provides a good example of <answer>compress</answer>ion artifacts.
Randomness and sharp attacks are two reasons that may make it harder to to do what to an audio file?
compress