Low or No Background Audio ensures that prerecorded speech remains clear and intelligible, without being disrupted by background sounds such as music, ambient noise, or effects.
When speech is mixed with competing audio, many users struggle to separate spoken words from background sound. Even when speech is technically audible, overlapping noise can make it exhausting or impossible to understand.
This criterion exists to ensure that speech-based content can be understood without relying on perfect hearing or advanced audio processing.
WCAG Success Criterion
1.4.7 Low or No Background Audio (Level AAA)
For prerecorded audio-only content that:
- Contains primarily speech in the foreground
- Is not an audio CAPTCHA or audio logo
- Is not vocal content intended as musical expression (such as singing or rapping)
At least one of the following conditions must be met:
- The audio contains no background sounds, or
- The background sounds can be turned off, or
- The background sounds are at least 20 decibels quieter than the foreground speech, except for brief sounds lasting one or two seconds
A 20 dB difference means the background audio is approximately four times quieter than the speech.
What Counts as Background Audio
Background audio includes any sound that is not the primary spoken content, such as:
- Music tracks
- Ambient noise (crowds, traffic, nature sounds)
- Sound effects
- Environmental audio layered beneath speech
This criterion applies only when speech is the main source of information. Content intended to be musical or artistic is excluded.
Why This Matters
Many people who are hard of hearing have difficulty separating speech from background sound, even when volume levels are increased. Hearing aids and assistive listening devices often amplify all sounds, not just speech, which can make background noise more disruptive rather than less.
When background audio competes with speech:
- Words blur together
- Speech becomes tiring to follow
- Users may miss key information
- Increasing volume does not resolve the problem
Even when speech sounds “clear enough” to the content producer, it may still fail intelligibility for users with hearing loss.
Reducing or eliminating background sound allows users to focus on speech without cognitive strain or repeated listening.
Who This Helps
This criterion primarily supports users who:
- Are hard of hearing
- Use hearing aids or cochlear implants
- Experience auditory processing difficulties
- Have age-related hearing loss
- Rely on clear speech for comprehension
Clear speech also benefits users listening in noisy environments or using low-quality speakers or headphones.
How to Meet This Requirement
There are three acceptable ways to meet this criterion:
No background audio
Speech is presented on its own, without competing sounds.
User control
Background sounds are present but can be turned off independently of the speech.
Sufficient separation
Background audio is mixed at least 20 dB below the speech, ensuring it does not interfere with intelligibility.
Occasional brief sounds, such as a door closing or notification tone, are allowed if they last no more than one or two seconds.
What This Criterion Does Not Apply To
This success criterion does not apply to:
- Audio CAPTCHAs
- Audio logos or brief branding sounds
- Music, singing, or rapping, where vocals are part of the musical expression
- Video content (covered by other success criteria)
It applies specifically to prerecorded, audio-only speech content.
Common Failures
Common failures include:
- Narration played over continuous background music
- Podcast-style content with loud ambient tracks
- Training audio with sound effects mixed too close to speech
- No option to disable background audio
- “Atmospheric” noise added for style rather than clarity
A common misconception is that slightly lowering background volume is sufficient. If the difference is not significant, users may still be unable to distinguish speech.
Rule Description
Prerecorded audio content that primarily contains speech must not include background audio that interferes with understanding. Background sound must be absent, user-controllable, or sufficiently quieter than the speech.
The Algorithm
- Identify prerecorded, audio-only content
- Confirm that speech is the primary information source
- Check for background audio
- If background audio exists, verify one of the following:
- It can be turned off, or
- It is at least 20 dB quieter than speech
- If none of these conditions are met, the criterion fails
Wrapping Up
Low or No Background Audio is about prioritising clarity over atmosphere. When speech conveys information, clarity is not optional; it is accessibility. Removing or sufficiently reducing background sound ensures that users who are hard of hearing can understand spoken content with confidence, without strain, repetition, or guesswork.
Level AAA sets a high bar, but when speech matters, clean audio is essential.
