What is a Decibel (dB)?

A decibel (dB) is the unit used to measure sound level on a logarithmic scale, used at events to set safe volumes, protect hearing and meet noise limits. When engineers and licensing officers talk about how loud a show is, they mean its sound pressure level in decibels.

How the decibel scale works

Because the scale is logarithmic, small numbers mean big changes:

  1. +3 dB: doubles the sound energy, a small but noticeable step.
  2. +10 dB: ten times the energy, and sounds roughly twice as loud.
  3. Measurement: sound level meters at the mix position and site boundaries record levels during the show.
  4. Weighting: readings are usually taken as dB(A), which matches how the ear hears, or dB(C), which captures more bass.

The sound engineer mixes to an agreed level, and noise conditions often set limits for the whole site. Crescat for music venues keeps each show's technical details together for the team.

dB(A) vs dB(C)

dB(A) reduces the weight of very low and very high frequencies, matching how people hear at normal levels. dB(C) includes much more of the bass. Outdoor events often have limits in both, because bass travels further and causes most neighbour complaints.

Typical sound levels

  • 30 dB: a quiet room
  • 60 dB: normal conversation
  • 85 dB(A): a level where long exposure starts to risk hearing
  • 95–105 dB(A): a typical rock or pop concert at the mix position
  • 120 dB and above: the threshold of pain

Frequently asked questions

How loud is a concert in decibels?

Most concerts run at around 95–105 dB(A) at the mix position, and louder near the speakers. Many venues and festivals set a maximum level for the mix position, often averaged over 15 minutes.

What decibel level damages hearing?

Risk depends on level and time. Long exposure above about 85 dB(A) can damage hearing, and the safe time halves with every 3 dB increase. Crew in loud areas wear hearing protection, and UK employers must manage this under noise at work regulations.

Why do festivals have noise limits?

Licensing authorities set limits to protect people living nearby. Levels are measured at the site boundary or at nearby homes, and repeated breaches can lead to fines or the loss of the event's licence.

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