Sound Check, EQ, and volume limit settings on iPhone
Change the way music sounds on iPhone
Choose an equalization (EQ) setting: Go to Settings > Music > EQ.
EQ settings generally apply only to music played from Music, but they affect all sound output.
Set a volume limit: Go to Settings > Music > Volume Limit.
To prevent changes to the volume limit, go to Settings > Screen Time > Content & Privacy Restrictions. Turn on Content & Privacy, tap Volume Limit, then tap Don’t Allow.
Normalize the volume level of your audio: Go to Settings > Music, then turn on Sound Check.