Principle 1 Perceivable · Guideline 1.4: Distinguishable
1.4.7 Low or No Background Audio
Background sound in speech recordings is quiet or can be turned off.
What this means in practice
Music under a voice makes comprehension much harder with reduced hearing. The standard names 20 dB of separation – roughly: the background must be clearly quieter than the voice.
Normative wording
The binding text lives at the W3C. What you read here is our own faithful rendering – not a quotation.