Last Updated 6 hours ago
Filmmaking Dictionary: Number 0 / 0 VU
Definition
0 VU is the nominal reference mark on a volume-unit meter. It indicates the operating level to which that meter has been aligned. It does not mean silence, and it is not automatically the maximum level the equipment can handle.
A VU meter responds relatively slowly compared with a peak meter. It gives a useful indication of sustained programme level, but it does not show every brief transient at its full peak value.
What Does 0 VU Equal?
The answer depends on calibration. On much professional analogue equipment, 0 VU is aligned to +4 dBu. Other equipment and software meters can use different references. A VU plug-in may allow the user to choose which digital level produces a zero reading.
The relationship should be stated, for example: “0 VU corresponds to a −20 dBFS reference tone in this system.” The two readings can then describe the same tone on different scales. There is no universal rule that every VU meter and digital recorder share that alignment.
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Using Tone to Align a Mixer and Recorder
- Identify the required reference: Use the production or delivery specification and the equipment’s documentation.
- Check the connections: Confirm mic/line input modes and the mixer’s output setting before adjusting level.
- Send a steady reference tone: A 1 kHz tone is commonly used for this purpose.
- Match the specified readings: Adjust the appropriate receiving level or calibration control.
- Return to programme audio: Check speech and louder transients with suitable peak metering and headphones.
Tone is steady, so a VU meter can settle on a clear reading. Dialogue is much less uniform. A syllable, clap or impact may produce a high peak while the VU indication remains modest.
Example of Available Headroom
Suppose a particular signal path is aligned so that a steady tone reading 0 VU also reads −20 dBFS on the recorder. That tone is 20 dB below digital full scale. It does not follow that all dialogue reading near 0 VU has the same peak margin: its momentary peaks can sit much higher than the meter’s slow indication suggests.
This is why a VU meter can be useful for judging operating level while a peak meter answers a different question. Both can be correct even when their needles or bars show noticeably different numbers.
Common Misunderstandings
- 0 VU is not 0 dBFS. Their relationship must be established.
- +4 dBu is common, not universal. Read the equipment specification.
- A VU reading is not a LUFS measurement. Do not use it alone to certify modern loudness delivery requirements.
- A VU-style graphic is not proof of meter compliance. Software and hardware displays may implement different response characteristics.
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Frequently Asked Questions
Is a brief reading above 0 VU always clipped?
No. The actual overload point depends on the equipment and signal path. Check peak levels and listen.
Can two VU meters show different readings for the same signal?
Yes, if their calibration, placement in the signal chain or response differs.
Related Terms
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