Low or No Background Audio
Tier 1 · The normative floor
Baseline compliance
What the normative text of WCAG 2.2 requires, and nothing more. Only a failure of this tier is a WCAG failure.
The bare minimum
For prerecorded audio-only content that is mainly foreground speech (not an audio CAPTCHA, audio logo, or singing or rapping), one of these is true: there are no background sounds, they can be turned off, or they are at least 20 decibels quieter than the speech, apart from occasional sounds of one or two seconds.
Normative text
Verbatim from WCAG 2.2, W3C Recommendation 12 December 2024. Underlined terms are defined below.
For prerecorded audio-only content that (1) contains primarily speech in the foreground, (2) is not an audio CAPTCHA or audio logo, and (3) is not vocalization intended to be primarily musical expression such as singing or rapping, at least one of the following is true:
- No Background
- The audio does not contain background sounds.
- Turn Off
- The background sounds can be turned off.
- 20 dB
- The background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sounds that last for only one or two seconds.
Definitions used (3)
Glossary definitions are normative. Their notes are informative.
- prerecorded
-
information that is not live
- audio-only
-
a time-based presentation that contains only audio (no video and no interaction)
- CAPTCHA
-
initialism for "Completely Automated Public Turing test to tell Computers and Humans Apart"
Informative notes (2)
CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file.
A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University.
Notes in the criterion Informative
WCAG 2.2 lists notes among its informative material, which "does not create requirements that impact a conformance claim." They help interpret the criterion but are not part of the floor.
Per the definition of "decibel," background sound that meets this requirement will be approximately four times quieter than the foreground speech content.
Tier 2 · The gap
Usability & user impact
Where content can meet this criterion and still make things harder for people with disabilities. These are not failures of SC 1.4.7, so raise them as usability defects. Known failures, including failures of related criteria, are listed in Tier 1.
Even background music at 20dB lower can make speech hard to follow for people with hearing loss.
Tier 3 · The golden path
Recommended best practice
The pattern that meets the floor, closes the gap, and avoids audit disputes. A recommendation, not a requirement.
Keep spoken-word recordings free of background music, or offer a speech-only version.
W3C's Understanding document and techniques for SC 1.4.7 ↗ are informative: sufficient techniques show ways to pass, and documented failures show common ways to fail, but neither changes what the criterion requires.
How SC 1.4.7 maps to the WCAG 3 draft
From this site's reviewed map to the WCAG 3 editor's draft. It's an interpretation: W3C has not published a mapping.
No provision in the current draft covers background audio levels.
From WCAG 2.2, section 5.1: “The main content of WCAG 2.2 is normative and defines requirements that impact conformance claims. Introductory material, appendices, sections marked as "non-normative", diagrams, examples, and notes are informative (non-normative). Non-normative material provides advisory information to help interpret the guidelines but does not create requirements that impact a conformance claim.”