The live meter below is preset to C-weighting. Switch to A or Z in Advanced Controls at any time.
What Does dBC Mean?
dBC is a decibel value after a C-weighting filter. Unlike A-weighting, C is much flatter — it keeps most low-frequency energy and mainly rolls off the very lowest octaves. At high sound levels the ear's response itself flattens, so C better matches perception for loud sounds (typically above 90–100 dB).
Some standards express peak limits in dBC (e.g. 140 dBC in workplaces). For general environmental noise and exposure guidance, the standard remains dBA; dBC answers a different question: how much low-frequency energy is present? See weighting curves and math.
When to Use a dBC Meter
- Music venues, nightclubs, concerts, subwoofer systems — where bass is the point.
- Engines, HVAC plant, industrial machinery, construction equipment.
- Any case where you suspect low-frequency dominance and want to quantify it.
- When comparing against a limit or prior measurement explicitly stated in dBC.
dBA vs dBC — The Diagnostic Comparison
Measure the same sound at the same spot twice — once in dBA, once in dBC:
- Small difference (0–3 dB): broadband sound — no strong bass bias.
- Large difference (≥10–15 dB): bass-dominated sound — low frequencies contribute heavily (e.g. subwoofer, diesel engine). This is the key insight C-weighting provides.
Note the suffix when recording: "82 dBA / 97 dBC at 1 m" is meaningful; "82 dB" alone is not.
How to Measure dBC Here
- Open the meter and select C-weighted in Advanced Controls → Frequency Weighting.
- Measure 30–60 s minimum; use average / Leq for overall level, peak for impulse highs. Keep distance and position documented.
- Repeat in A-weighting without moving the device to get the dBA vs dBC diagnostic.
- Calibrate for consistency (guide). Phone mics under-report deep bass, so C readings remain estimates — better for comparison than absolute certitude.
Limitations
- Consumer phone microphones are speech-optimized and attenuate low bass; C-weighted values still under-report true low-frequency SPL vs. a lab mic. Treat as comparative, not certified.
- Above ~100 dB many phone mics clip; below ~30 dB the noise floor dominates.
- Pre-browser DSP may remain active on some devices. See Accuracy and Validation.
FAQ — dBC Meter
What is C-weighting?
When should I choose dBC over dBA?
Is dBC louder than dBA?
Related: dBA Meter · Frequency Analyzer · Audio Spectrum Analyzer · dB vs dBA guide