What it does
Hyper Voice is a Normal-type Special move, 90 base power, 100% accuracy. Two things set it apart in doubles.
First: it's a sound move, which means it hits through Substitute. If the opponent has a Substitute up, your Hyper Voice bypasses it and deals direct damage. Not the most common interaction, but when it triggers it's immediate value.
Second, and more impactful: Pixilate converts Normal-type moves into Fairy-type moves with a 20% power bonus. On Sylveon, that turns Hyper Voice into a Fairy-type spread move with roughly 108 equivalent power. It hits Dragon, Dark, and Fighting for super-effective. The Normal-to-Fairy conversion is what makes this move competitively relevant at high level.
The key doubles mechanic: Hyper Voice hits both opposing Pokémon simultaneously. One move, full coverage of both target slots, no target selection needed. Every turn you fire it, both opponents take Fairy-type spread damage.
Who runs it
Sylveon (100%): Every Sylveon in Champions data runs Hyper Voice. It's the primary spread STAB, full stop. 155 base Sp. Atk., 130 Sp. Def., and Hyper Voice is the main reason it's in the lineup.
Primarina (99%): 126 Sp. Atk. and it has Liquid Voice, which converts all sound moves to Water-type. So Primarina's Hyper Voice deals Water-type spread damage, not Fairy. Same spread coverage mechanic, different type. Gives it a 100% accurate Water-type spread move alongside its Water/Fairy typing.
Farigiraf (60%): 110 Sp. Atk. Runs Hyper Voice for reliable Normal-type spread pressure while providing speed control and field support.
Aurorus (68%): 99 Sp. Atk. Hyper Voice fills the spread Normal damage role in snow teams, complementing Blizzard for a dual spread output package.
Heliolisk (43%): 109 base Speed. Hyper Voice gives it spread chip damage outside of its Electric STAB.
How to use it
Hyper Voice's usage is direct: fire it when you want to apply spread pressure to both opposing Pokémon. You don't pick a target. The move does the work.
For Sylveon, the standard read is: Hyper Voice for spread turns, Moonblast when you have one specific priority target to eliminate. Both are Fairy-type, but Moonblast deals more to a single target while Hyper Voice pressures both sides. When the opposing spread needs addressing — two Pokémon both posing threats — Hyper Voice is the better call. When one Pokémon is the problem, Moonblast finishes it faster.
The Substitute pierce works cleanly: opponents setting up a Substitute are usually building toward a setup turn. Hyper Voice starts chipping through before the setup completes. With Sylveon's Sp. Atk., a Substitute losing one full Hyper Voice hit either breaks or drops to a value where a second attack ends it next turn.
Tips & strategy
Spread coverage creates an inherent pressure advantage: opposing switches don't save the incoming Pokémon from the first Hyper Voice. Whatever comes in gets hit immediately. That constant two-slot pressure makes rotating around Sylveon more difficult.
Watch for Soundproof: it's a complete immunity to all sound moves including Hyper Voice. Any Soundproof Pokémon on the opposing side takes zero damage from the move, regardless of type. When your read says Soundproof is in the matchup, have a non-sound option ready.
The Pixilate line (Sylveon) and the Liquid Voice line (Primarina) both turn Hyper Voice into STAB spread damage, just in different types. Build around whichever type coverage fits your team. Fairy spread fills in Dragon/Dark/Fighting, Water spread synergizes with rain.