When a Pokémon is released from its Poké Ball, it will call out its
cry, which consists of an electronically made "noise". It will also
cry out when using certain moves, such as Growl, Roar, and Hyper
Voice. If the Pokémon faints or comes into battle when injured during
Generation III and later, the cry will sound, but it will be altered
slightly. The cry is also changed noticeably when a Pokémon is sent
into a battle with a status ailment. Pokémon with evolutionary
relations to each other (such as Charmander and Charmeleon) will often
have notably similar cries, though others may sound very different
(such as Kirlia and Gallade). - Bulbapedia
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