v. perked, perkÂ·ing, perks. v.intr. 1. To stick up or jut out: dogs' ears that perk. 2. To carry oneself in a lively and jaunty manner.
However instead of crests and troughs, longitudinal waves have compressions and rarefactions. Definition 1: Compression. A compression is a region in a longitudinal wave where the particles are closest together. A rarefaction is a region in a longitudinal wave where the particles are furthest apart. As seen in Figure 1, there are regions where the medium is compressed and other regions where the medium is spread out in a longitudinal wave. The region where the medium is compressed is known as a compression and the region where the medium is spread out is known as a rarefaction.
Compression may be lossless compression, in which all of the information in the original data is preserved, and the original data may be recovered in form identical to its original form; or lossy compression, in which some of the information in the original data is lost, and decompression results in a data form slightly different from the original.