Longitudinell våg - Compression and rarefraction

In a displacement against distance graph, how would one determine when there is a compression or a rarefaction? Also, does the direction of the longitudinal wave change the point we perceive as when the compression or rarefaction occur?

Kan de uteblivna svaren bero på svår engelsk nomenklatur?
Jag gissar så åtminstone någon kan rätta mig:

Compression: Increasing displacement
Rarefaction: Decreasing displacement

Wave direction:
Compression occurs before rarefraction in a longitudinal wave

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