What is SPL (Sound Pressure Level)?

SPL (sound pressure level) is the measured loudness of sound at a given point, expressed in decibels (dB), and is used at live events to manage audience safety, noise limits and the mix. At gigs and festivals, SPL is usually measured at the front of house mix position and at the site boundary.

How SPL is managed at live events

Managing SPL follows a routine that starts long before doors:

  1. Agree the limits: the venue, local authority or licence sets the maximum levels for the audience and at neighbouring homes.
  2. Set up the system: the system tech aligns the PA so coverage is even and the front rows are not far louder than the mix position.
  3. Measure: a calibrated SPL meter logs levels during the show, often averaged over 15 minutes.
  4. Display: engineers watch live readings at the desk so they can stay within the limit.
  5. Report: the logs are kept as a record that the event complied with its licence.

Music venues with strict limits often share them with visiting engineers in the advance, so the tour knows the rules before arrival. Crescat supports this for music venues managing visiting productions.

SPL vs decibel

The decibel is the unit; SPL is what is being measured. A reading of "100 dB SPL" means a sound pressure level of 100 decibels. Readings are often weighted: dB(A) follows how the ear hears mid and high frequencies, while dB(C) includes more bass, which matters for off-site noise from festivals.

Typical SPL levels and limits

  • Normal conversation: about 60 dB(A)
  • Busy pub with music: about 85–90 dB(A)
  • Rock concert at the mix position: about 98–103 dB(A), averaged
  • WHO recommended maximum for venues and events: 100 dB(A) averaged over 15 minutes
  • UK workplace noise action values for staff: 80 and 85 dB(A) daily exposure

Frequently asked questions

Is there a legal SPL limit for concerts?

It depends on the country. Some, such as Switzerland, set legal audience limits. In the UK there is no single audience limit, but licences often include noise conditions, and the Control of Noise at Work Regulations protect staff and crew.

Where should SPL be measured?

Usually at the front of house mix position, with the reading related to the loudest audience area. Off-site levels are measured at the nearest homes or other noise-sensitive places. Festivals often hire a noise consultant to do this.

How do you protect hearing at loud events?

Keep levels within limits, offer earplugs to the audience, give crew hearing protection, and create quieter areas away from the stages. In-ear monitors also help performers reduce their own exposure.

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