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Perceivable WCAG 1.4.7

1.4.7 Low or No Background Audio

For prerecorded audio-only content containing speech, background sounds are at least 20 dB lower than foreground speech, or can be turned off.

Level AAA Moderate WCAG 2.0 (new) WCAG 2.1 WCAG 2.2

What This Rule Means

WCAG 1.4.7 applies to prerecorded audio content that primarily contains speech, such as podcasts, narrated videos, or recorded presentations. When background sounds (music, ambient noise, sound effects) are present alongside speech, those background sounds must be at least 20 decibels quieter than the foreground speech content. Alternatively, a mechanism can be provided to turn off background sounds entirely.

A 20 dB difference means the background audio is approximately four times quieter than the speech. This ensures that people with hearing difficulties can distinguish the spoken words from background noise. The criterion does not apply to audio that is primarily musical in nature or to live audio.

Why It Matters

People with hearing impairments, auditory processing disorders, or those who are hard of hearing struggle significantly when background audio competes with speech. Even moderate background music can mask speech frequencies and make content incomprehensible for these users. The 20 dB separation provides enough clarity for most users with hearing difficulties to follow spoken content.

This also benefits non-native speakers and users in noisy environments who need clear speech to understand content.

Related axe-core Rules

There are no automated axe-core rules for 1.4.7. This criterion requires manual audio analysis because automated tools cannot measure the relative volume of foreground speech versus background audio. Professional audio editing software with level meters is needed.

How to Test

  1. Listen to the audio content and note whether background sounds are present alongside speech.
  2. If background sounds exist, use audio analysis software (such as Audacity) to measure the dB levels of speech and background separately.
  3. Verify the background is at least 20 dB lower than the speech peaks.
  4. Alternatively, check if a mechanism exists to disable background audio while retaining speech.
  5. Have someone with hearing difficulty listen and confirm the speech is clearly distinguishable.

How to Fix

During audio production, set background levels appropriately:

/* Audio mixing guidelines (conceptual, not code) */
/* Speech track: -12 dBFS to -6 dBFS (target peak) */
/* Background music: -32 dBFS to -26 dBFS (at least 20 dB below speech) */
/* Sound effects: -28 dBFS or lower during speech segments */

<!-- Provide separate audio tracks when possible -->
<audio controls>
  <source src="narration-only.mp3" type="audio/mpeg" />
</audio>
<label>
  <input type="checkbox" id="bg-audio-toggle" />
  Enable background music
</label>

Use audio ducking to automatically lower background audio during speech segments. In production workflows, apply sidechain compression so that speech triggers background level reduction.

Common Mistakes

  • Background music at the same level as narration, making speech hard to distinguish for hearing-impaired users.
  • Ambient sound effects that spike during speech, temporarily masking words.
  • Podcast intros with loud music that continues at the same volume önce speech begins.
  • No option to disable background audio when separate tracks are technically available.
  • Applying this requirement to primarily musical content, which is actually exempt.

Resources