In professional audio, measuring sound correctly is as important as making it. From decibel SPL in room acoustics to LUFS in broadcast loudness, understanding sound measurement units is essential for engineers, producers, and content creators.
Sound Pressure Level (SPL)
SPL measures actual acoustic pressure in the room, referenced to 20 µPa (threshold of hearing). Measured with a calibrated microphone and SPL meter.
Key SPL values: 0 dB SPL = hearing threshold, 30 dB = quiet library, 60 dB = conversation, 85 dB = prolonged exposure limit (OSHA), 120 dB = pain threshold, 140 dB = jet engine.
In studio design, background noise should be below NC-15 (Noise Criterion) — approximately 20–25 dBA — for critical listening environments.
The LUFS Standard for Loudness
LUFS (Loudness Units relative to Full Scale) is the modern standard for measuring perceived loudness in broadcast and streaming. Unlike peak levels, LUFS accounts for how humans actually perceive loudness over time.
- Streaming targets: Spotify: −14 LUFS, Apple Music: −16 LUFS, YouTube: −14 LUFS
- Broadcast: EBU R128 (Europe): −23 LUFS. ATSC A/85 (US): −24 LKFS (same thing, different name)
- Podcast: Typically −16 to −19 LUFS
dBFS vs dB SPL vs LUFS
dBFS (decibels Full Scale): Digital measurement. 0 dBFS is the maximum level before clipping. All values are negative. A signal at −6 dBFS is half the maximum digital level.
dB SPL: Physical acoustic measurement. Depends on monitor volume and room. The same −6 dBFS signal could be 70 dB SPL or 100 dB SPL depending on your speaker volume.
LUFS: Perceived loudness, integrating frequency weighting and time averaging. Two tracks at the same LUFS will sound equally loud to listeners, even if their peak levels differ.
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