Read this: With too low a bit rate, compression artifacts (i.e., sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to compress because of its randomness and sharp attacks. When this type of audio is compressed, artifacts such as ringing or pre-echo are usually heard. A sample of applause compressed with a relatively low bit rate provides a good example of compression artifacts.

Other than pre - echo, what is another example of what can happen when audio is compressed?
What is the answer? (If it cannot be answered, return "unanswerable")
ringing