Last Updated 6 hours ago
Filmmaking Dictionary: Number 0 / 0 dB
Definition
0 dB means that the measured quantity equals the stated reference. When a gain control is set to 0 dB, it usually indicates unity gain at that stage: the signal is neither increased nor reduced by that control.
It does not automatically mean silence, maximum recording level or a particular sound-pressure level. A decibel measurement only becomes useful when you know what is being compared.
Why Zero Can Still Be Loud
Decibels describe a ratio on a logarithmic scale. A ratio of one to one is 0 dB. If an audio clip enters a unity-gain stage, it leaves at the same level, whether that clip contains a whisper, a loud impact or room tone.
For an amplitude ratio, the calculation is 20 × log₁₀(output ÷ input). With equal nonzero amplitudes, output ÷ input equals 1, and log₁₀(1) equals 0. This is why zero gain change is different from zero signal.
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A Fader Example
A recorded line of dialogue peaks at −12 dBFS. A simple fader set to 0 dB leaves that peak at approximately −12 dBFS. Raising the fader by 6 dB moves it to approximately −6 dBFS; lowering it by 6 dB moves it to approximately −18 dBFS, assuming no other processing changes the signal.
The fader’s 0 dB mark and the meter’s 0 dBFS mark therefore mean different things. One specifies a gain change; the other identifies digital full scale.
Read the Suffix
- 0 dB gain: No level change through the control or stage being described.
- 0 dBFS: The digital full-scale reference used by audio meters and files.
- 0 dBu: An electrical level of approximately 0.775 volts RMS.
- 0 dBV: An electrical level of 1 volt RMS.
- 0 dB SPL: A sound-pressure reference, not the absence of acoustic energy.
Where Confusion Causes Problems
“Set it to zero” is incomplete when matching a mixer to a camera. The mixer may have a fader marked in gain, a VU meter with an alignment reference, and an output specified in dBu. The camera may show dBFS. Setting every visible number to zero does not align those systems.
Instead, identify the output and input settings, send the agreed reference tone, and compare the specified meter readings. Then check actual dialogue and transients. A successful tone check does not guarantee that a performer’s loudest delivery will remain within the system’s headroom.
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Frequently Asked Questions
Does 0 dB on a fader mute the track?
No. It normally leaves its level unchanged. Mute or the bottom of the fader’s range performs a different function.
Does unity gain mean the equipment adds no noise or distortion?
No. It describes level change. A physical device can still contribute noise, distortion or other processing.
Can a camera show 0 dB gain?
Yes. Some cameras express image gain in decibels. That setting is relative to the camera’s reference sensitivity and should not be confused with its audio meters.
Related Terms
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