Ever been vibing to a chill acoustic track on your iPhone, only for the next song to blast your eardrums into another dimension? It’s jarring. Honestly, it’s one of those small digital annoyances that can ruin a workout or a morning commute. This is exactly why Apple built a feature called Sound Check.
Most people stumble upon it in their settings and wonder if it's some kind of EQ or a secret "pro" audio hack. It's actually much simpler than that, but there's a lot of debate among audiophiles about whether you should actually leave it on.
Basically, Sound Check on iPhone is a normalization tool. Its only job is to make sure every song in your Apple Music library plays at roughly the same volume level. It stops that frantic scramble for the volume buttons when moving between an older, quieter jazz record and a modern, ultra-loud pop hit.
How Sound Check actually works under the hood
When you toggle this on, your iPhone doesn't actually go into your music files and change the "DNA" of the song. It isn't editing your files. Instead, the Music app scans your library and calculates the average loudness of each track.
📖 Related: Transfer Pictures from iPad to Desktop: What Most People Get Wrong
It uses something called metadata.
When a song plays, the app looks at a small tag attached to the file that says, "Hey, this song is recorded at -10dB," and it adjusts the gain accordingly. If the next song is recorded at a much higher level, your iPhone automatically nudges the playback volume down so the two tracks sound consistent. It’s like having a tiny sound engineer living inside your phone who moves the slider for you before every song starts.
Apple targets a loudness of about -16 LUFS (Loudness Units relative to Full Scale). If you're coming from Spotify, they usually target -14 LUFS, which is why Apple Music often feels "quieter" than other apps if you have this setting turned on.
👉 See also: Cómo Conseguir un Número de Nueva York: Realidades de los Prefijos 212, 646 y 332
Why some people hate it (The "Audiophile" Perspective)
There is a massive divide on Reddit and audio forums about this. Some users swear that turning Sound Check off makes the music sound "fuller" or "punchier."
Is it a placebo? Kinda.
When you turn Sound Check off, tracks that were mastered to be loud will play at their full, aggressive volume. Humans naturally perceive "louder" as "better quality." When Sound Check brings a loud track down to match a quiet one, it can feel like the "life" has been sucked out of the song.
However, experts like those at Apple Digital Masters argue that Sound Check doesn't actually touch the dynamic range. It doesn't squash the peaks and valleys of the audio—it just lowers the whole thing. Imagine a photo: normalization is like turning down the brightness of the entire screen, whereas compression (which Sound Check doesn't do) would be like messing with the contrast until the shadows and highlights are all the same grey.
Sound Check and Dolby Atmos: A weird relationship
If you’re a fan of Spatial Audio or Dolby Atmos, Sound Check is almost a requirement. Atmos tracks are inherently much quieter than standard stereo tracks because they need more "headroom" for the 3D positioning of sound.
Without Sound Check, you might find yourself cranking the volume to 80% to hear an Atmos mix, only for a 2005 stereo rock song to come on next and absolutely destroy your speakers. For this reason, many Atmos listeners keep it on to bridge that massive volume gap.
How to turn it on (or off)
If you want to try it out for yourself, the process is pretty buried in the iOS menus.
- Open the Settings app on your iPhone or iPad.
- Scroll way down until you find Music. (In some iOS versions, you might need to tap Apps first, then Music).
- Look for the Audio section.
- Toggle the Sound Check switch.
It’s an instant change. You don't need to restart the app or your phone. Just play a few songs from different eras—like something from the 70s followed by a 2024 EDM track—and you’ll hear the difference immediately.
Real-world impact on your battery and data
You might be wondering if this extra "scanning" kills your battery. Short answer: no. The loudness data is usually already there or calculated once and stored. It doesn't use extra data to "check" the sound, and the processing power required to nudge a volume slider is so microscopic that your battery won't even notice it.
The verdict: Should you use it?
Whether you should keep it on really depends on how you listen to music.
If you are an "album purist" who listens to one record from start to finish, turn it off. The artist already decided how loud each song should be relative to the others on that album. Sound Check can sometimes mess with the intentional "ebb and flow" of a concept album.
But if you are a "playlist person" who shuffles 500 songs from 50 different genres? Keep it on. It saves your hearing and prevents those annoying volume jumps that make you jump out of your skin.
Actionable Next Steps
- Check your current setting: Most iPhones have this off by default. Go to Settings > Music and see where you stand.
- Test with Atmos: If you notice your Dolby Atmos songs are way quieter than your regular music, turn Sound Check ON. It’s the easiest fix for the "quiet Atmos" problem.
- Compare the "Punch": Turn it off for five minutes and listen to your favorite high-energy song. If it suddenly feels like the bass has "woken up," you might prefer the raw, un-normalized sound, even if it means manual volume adjustments later.
- Ear Safety: If you often listen to music to fall asleep or while focusing, turn it ON. It prevents accidental "volume spikes" that can wake you up or break your concentration.