OpenMontage/skills/creative/sound-design.md

Sound Design for Video Production

Sources: W3C accessibility standards, BBC audio guidelines, YouTube/TikTok platform specs, Sweetwater mastering guides, ElevenLabs documentation, Boris FX, HookSounds, Artlist

Quick Reference Card

DIALOGUE:       -12 dB peak  |  -16 to -14 LUFS integrated
MUSIC BED:      -30 to -20 dB (18-20 dB below dialogue)
SFX:            -18 to -12 dB (6 dB below dialogue minimum)
WHOOSH TIMING:  Start 10-20ms before visual, duration 400-500ms
MUSIC BPM:      Calm 60-80 | Standard 90-110 | Upbeat 120-140
TRUE PEAK:      Never exceed -1.5 dBTP
VOICE EQ:       HPF 80Hz, cut 500Hz, boost 2-5kHz, cut 6-8kHz
VOICE COMP:     3:1 ratio, 1-5ms attack, 10-20ms release
TARGET LUFS:    -14 LUFS (YouTube/TikTok/IG) | -16 LUFS (podcasts)

Audio Ducking Levels

Element	Peak Level	Notes
Dialogue / Narration	-6 dB to -12 dB	Primary element
Background music (during speech)	-18 dB to -20 dB	18-20 dB below dialogue
Sound effects	-12 dB to -18 dB	Between dialogue and music
Final mix	-10 dB to -20 dB	Never exceed 0 dB

Ducking rules:

• W3C accessibility: music must be 20 dB lower than foreground speech
• BBC guideline: lower music by an additional 4 dB from where you think it sounds right
• Duck music 6-12 dB when narration is active; for complex educational topics, duck up to 22 dB
• EQ trick: cut 2-4 kHz on background music to make room for speech clarity
• When testing, adjust in 1 dB increments from a -20 dB baseline upward

Music Selection by Content Type

Content Type	BPM Range	Mood
Calm explainer / tutorial	60-80	Contemplative, focused, trust-building
Corporate / testimonial	60-100	Professional, calm, credible
Standard explainer / educational	90-110	Steady, engaging, not distracting
Upbeat explainer / promo	110-130	Enthusiastic, approachable
High-energy / product demo	120-140	Exciting, urgent, dynamic
Action / fast-paced	140-200	Adrenaline, intensity

Genre recommendations for explainers:

• Lo-fi (steady, non-distracting, modern feel)
• Ambient (atmospheric, stays in background)
• Light acoustic guitar instrumentals (warm, approachable)
• Contemporary pop instrumentals (upbeat, familiar)
• Inspiring soundtrack / cinematic light (builds emotion without overwhelming)

Key rules:

• Always use instrumental tracks when voiceover is present — lyrics compete with narration
• Choose dynamically even tracks — avoid dramatic crescendos or beat drops
• Match energy to the learning context: upbeat for "exciting new concept," gentle for serious topics

Sound Effects (SFX) Placement

SFX Categories for Explainer Videos

SFX Type	Use Case	Duration	Level
Whoosh / Swish	Scene transitions, slide changes	400-500ms	-18 to -12 dB
Pop / Pluck	Text appearing, bullet points	<200ms	-15 to -12 dB
Click / Tap	UI interactions, button presses	<100ms	-20 to -15 dB
Riser / Swell	Building to a reveal or key point	1-3s	-18 to -12 dB
Impact / Hit	Key reveal, important stat	<300ms	-12 to -6 dB
Subtle whoosh	Element sliding in/out	200-400ms	-20 to -15 dB

Timing rules

• Start whoosh 10-20ms before the visual transition (brain processes audio faster)
• Peak of whoosh energy should coincide with the moment of greatest visual change
• Fine-tune in 1-frame increments for sync
• When stacking whooshes, keep them in different frequency bands

Platform Loudness Targets (2025)

Platform	Integrated LUFS	True Peak	Notes
YouTube	-14 LUFS	-1.5 dBTP	Normalizes down, not up
YouTube Shorts	-14 LUFS	-1.5 dBTP	Same as long-form
TikTok	-14 LUFS	-1 dBTP	Prioritize 2-4 kHz for phone speakers
Instagram Reels	-14 LUFS	-1 dBTP	Same mobile optimization
Spotify	-14 LUFS	-2 dBTP	Stricter true peak
Apple Podcasts	-16 LUFS	-1 dBTP	More headroom for speech

Content-type LUFS

Content Type	Integrated LUFS	Dynamic Range
Dialogue-heavy / educational	-16 to -14 LUFS	6-12 dB
Music videos	-14 to -12 LUFS	6-10 dB
Gaming content	-14 to -12 LUFS	8-12 dB

Technical specs

• Sample rate: 48 kHz preferred
• Bit depth: 24-bit preferred
• Bitrate: 192 kbps minimum
• Noise floor: below -60 dB
• Headroom: at least -6 dB in the final mix

AI TTS (ElevenLabs) Mixing

Processing Chain

1. High-pass filter: 80-100 Hz (24 dB/oct slope) — removes rumble and low-frequency TTS artifacts
2. EQ:
   • Cut ~500 Hz: removes muddiness/boxy quality
   • Boost 2-5 kHz (+2-3 dB): adds presence and clarity
   • Cut 6-8 kHz (gentle): reduces sibilance/harshness common in AI voices
   • Optional: boost 120-250 Hz for thinner AI voices
3. Compression:
   • Ratio: 3:1 (range 2:1 to 4:1)
   • Attack: 1-5 ms
   • Release: 10-20 ms (increase to 30ms if pumping)
   • Threshold: -26 dB (target -4 to -6 dB gain reduction)
   • Output gain: +6 dB
4. De-esser: target 6-8 kHz if sibilance remains
5. Limiter: ceiling at -1.5 dBTP

AI-specific tips

• AI TTS has inconsistent dynamics — compression is more important than for human speech
• ElevenLabs may have subtle artifacts in 4-6 kHz; use narrow notch cut if detected
• Sidechain background music to voiceover track for automatic ducking
• Cut 2-4 kHz on the music bed to clear the "intelligibility band" for voice
• Always test on phone speakers — if voice disappears, boost 2-4 kHz more aggressively

Applying to OpenMontage

When the audio_mixer tool is used in the compose stage:

1. Set narration as primary track, music as secondary
2. Apply ducking: music -18 to -20 dB below narration during speech
3. Select music BPM from the table above based on the playbook mood
4. Place SFX at transition points with 10-20ms audio lead
5. Target -14 LUFS integrated for YouTube output
6. Keep true peak below -1.5 dBTP
7. For AI TTS narration, apply the processing chain above before mixing
8. Test the final mix on phone speakers — most viewers watch on mobile