Improved Management of PA System
L_eq Limits and Off-Site Annoyance

A loudness metering live event workflow for Public Address systems
using DirectOut Technologies PRODIGY

Jonathan J Digby

digbyphonic@gmail.com
Digbyphonic Ltd // University of Derby

2026-03-14

Context

It is commonplace for sound mixers and sound system engineers at live events to be required to operate the sound system within an enforced Sound Pressure Level limit.

This is usually displayed in the FOH mix area as a continuously updating A weighted time-averaged sound level.

A typical metric L_p_{, Aeq, 15 min} is an accumulated equivalent sound level of minutes passed.

An instant adjustment in sound system output level will not be reflected in the log until a rolling period has accumulated; in this case, fifteen minutes.

An example of a typical sound level limit:

\(100 \text{ dB }\textit{L}_{\textit{p,} \text{Aeq,15}\textit{ min}}\)

Note

A-weighted sound _pressure _equivalent to a Level of 100 decibels over a rolling 15 minute period.

Complication

A-weighting measures do not adequately represent human hearing at concert sound levels
A-weighting is narrowband; this does not adequately account for broadband variances in typical program content
Time-averaged measures are determined by past activity; the accumulated contribution of current show levels are not immediately represented
Loudness is not equivalent to Sound Pressure Level (SPL)

Figure A3.1 [1,p 76]

Figure A3.1 – Discrepancy in low-frequency contribution with A-weighted sound-level measurements. [1,p 76]

Loudness \(\not\equiv\) Sound Pressure Level (SPL)

Equal-loudness contours for sinusoidal tones or narrow-band noises indicate the interesting dependence of loudness on frequency.

However, loudness depends on many more variables such as bandwidth, frequency content, and duration.

Consequently, it is too simple to approximate loudness level by a single weighting such as the A-weighted sound pressure level.

Because A-weighting has a frequency dependence that corresponds to that of the equal-loudness contours at low levels, A-weighted sound pressure level approximates loudness level only for sinusoidal tones or narrow-band noises at lower levels.

Therefore, dB(A)-values of noises or complex tones, or combinations of both, are misleading when used as indications of subjectively perceived loudness.

Hugo Fastl & Eberhard Zwicker (2007). [2,p 205]

Kuttruff on Sound Pressure Level Meters

When such an instrument is applied to a sound signal with more complex spectral structure, the result may deviate considerably from the true loudness level.

The reason for such errors is the fact that, in our hearing, weak spectral components are partially or completely masked by stronger ones and that this effect is not modelled in the above-mentioned sound level meters.

Apart from masking in the frequency domain, temporal masking may occur in non-stationary signals.

In particular, a strong time-variable signal may mask a subsequent weaker signal.

This effect is very important in listening in closed spaces […].

A more fundamental shortcoming of the above-mentioned measurement of loudness level is its unsatisfactory relation to our subjective perception.

Heinrich Kuttruff (2009). [3,p 25]

Loudness \(\neq\) Volume \(\neq\) SPL/Amplitude/Gain

Loudness \(\neq\) Volume \(\neq\) SPL/Amplitude/Gain. The first is a perceptual quality, the second is a colloquial term loosely related to the others, and the third refers to physical quantities. [4–8]

Tim Ziemer (2024). [9,p 288]

The loudness of a sound, especially a complex sound containing many frequencies, has no simple relation to its sound pressure level, and it is hopeless to try to measure relative loudnesses of different sounds by using a sound level meter.

Glenn D White & Gary J Louie (2005). [5,p 222]

Solution

Concerts and events can optimize sound exposure within Sound Level Limits through the use of standard Audio Program Loudness Metering[10]
The result is real-time metering, and broadband loudness normalization, with parallel benefit for audience and stakeholders:
parity of loudness between acts and show elements using a fair and psychoacoustically correct balance[11–13]
This is not the case when operating solely to an A weighted and time-averaged Sound Level Limit;
the result of which is peak normalization, with inconsistent loudness for the audience between show segments.

Loudness Unit Ceiling
An industry-standard European Broadcast Union R 128 loudness meter[14] is used to calibrate the sound system’s acoustic gain to the desired SPL targets.
The term Target Level Loudness is used in EBU R128 for producing audio program to a common broadcast level.
In our case, this is transformed into a Loudness Unit Ceiling.[15]

Features

tried and tested real-time indication of program loudness levels; designed for ease of use by mix engineers
a psychoacoustically correct broadband measure
fair comparison of content loudness, which allows a fair apportioning of total sound energy
real-time compliance for all calibrated limits is ensured
loudness measures are an appropriate measure of annoyance [16]

— therefore, by extension, the reduced loudness variance will likely provide additional benefit
loudness and annoyance are linked for higher-level low frequency noise [17]

— therefore, reduced variance provided by this broadband loudness measure is likely to reduce annoyance
impulsive low frequency noise (‘bass beats’; ‘bass thump’) is a primary cause of off-site annoyance, and is typically troublesome to manage [18, 19]

— compliance with these off-site measures is ensured; alongside the additional benefit of reduced variance

The EBU R 128 Loudness Meter

EBU R 128 [14] is based upon the ITU BS.1770 Recommendation[20] but with some additional features
Loudness units (LK or LU) which are equivalent to a decibel
The most important feature is its Recommended Target level of –23 LUFS (Loudness Units Full Scale)
— in our context, this is transformed and interpreted as a Loudness Unit Ceiling
‘0 LU’ in ‘EBU mode’ \(=\) –23 LUFS
— therefore, the Loudness Unit Ceiling for a meter in ‘EBU mode’ is shown as 0 LU [21,p 12]
It’s a fixed Loudness Unit Ceiling which allows us to calibrate the overall acoustic gain of the system.
The Loudness Meter algorithm is full range (wide-band), which incorporates low frequency content
— therefore, the acoustic calibration applies to A or C weighting, and low-frequency octave-band limits [10,p 3, 19, 22, 23]
The Loudness Meter algorithm offers three distinct time scales [21,p 12]:

• Momentary Loudness (abbreviated “M”) — time window: 400 ms
• Short-term Loudness (abbreviated “S”) — time window: 3 s
• Integrated Loudness (abbreviated “I”) — from ‘start’ to ‘stop’

— therefore, the acoustic calibration applies to time averaged, impulse, or Fast / Slow measures [24]

Strategic use of EBU R 128 loudness metering

For a propagation test, a reference signal at the Loudness Unit Ceiling of 0,0 LU (–23,0 LUFS) is used to excite the sound system; the acoustic output (sound system gain) is adjusted to follow whatever L_p limits are in place: FOH, and off-site
For the duration of the event program Loudness Meters[25] measure the electrical signal output from each source, e.g. System 1, System 2, Presenters Desk, VT [10,p 7]; therefore, account is taken of any audience contribution to the acoustic SPL measures (i.e. measurement microphones at FOH)

Calibration can be made to any combination of the following measures:

continuous A-weighted sound level \((\textit{L}_{\textit{p,}\text{AS}})\)
time-averaged sound level \((\textit{L}_{\textit{p,}\text{eq,}\textit{T}})\), at any required weighting and interval \((T)\)
octave- or fractional octave-band measures, Fast or Slow
and so forth

PRODIGY — the all-in-one solution

It receives outputs from all sources, by default (mixing consoles, VT, etc.)
Separate computer(s) connect to the PRODIGY via network
— this allows separate instances of Globcon to generate shared or dedicated monitor displays with an EBU R128 meter for each console’s Left/Right signal
Remote meter displays should be positioned for clear and immediate line-of-sight for the mixing engineers*

— an umbilical cabled remote monitor on a tripod stand allows it to be moved in front of the active mix engineer
— it may help to consider this as a ‘speedometer’; and the driver must not breach the speed limit

It is important to remember that an SPL limit is not a target

Optional: provide the L_p_, Aeq, T alongside the mix engineer’s R 128 meter
— however, this may prove to be a distraction
— the mix engineer is encouraged to concentrate on the engineering, whilst respecting sensible electrical signal levels (VU, dBFS, LU, etc.)

Preparation

It is essential that all FOH operatives, production management and relevant stakeholders are informed about EBU R 128 in advance of the event to allow them time to prepare, discuss, and familiarize. [10,p 7]

For example, it is commonplace for digital mixing consoles to be used with preset templates (sessions, showfiles).
R 128 metering is widely available; therefore, through regular use a mix engineer is able to predict the Integrated Loudness level for their entire show in advance.‡

Appropriate definitions, descriptions, strategies, and guidance should be taken from the following EBU documents:

PRODIGY: Recommended Settings

Loudness Metering options:
- Levelmeter Stream = Full Speed (meter refresh rate must be as fast as possible)
- Mode = 4 Stereo (assign to L/R input from each source; labelled accordingly – e.g. console A LR, etc.)
- Unit = LU range (in LUFS mode our Loudness Unit Ceiling [Upper Limit] of –23 LUFS is not marked)
- Scale = EBU 9 dB (user may choose either range)
- Optional: display source SLOT dBFS meters alongside; however, the recommendation is to only display necessary meters on the remote monitor(s) — no clutter
An R 128 meter for each console’s input to PRODIGY should always be visible to the system engineer on their own local monitor
N.B.: If necessary the source output level to the sound system may be adjusted to a lower level than the maximum calibration:
— this could be for SPL compliance
— or, to allow the level to increase gradually throughout the day
— or, greater impact for a show segment: e.g. headline act

Example Screenshot

(i) Electrical Alignment Signal and Level

Ensure filtering and dynamic processing is bypassed on the mixing console output path
Adjust console operating level so that a \(1\) kHz sine wave at
–20 dBFS on Left output equals –20 dBFS at the Left input of the PRODIGY; or, note the headroom
Repeat for the Right channel (and any other signal paths, e.g. Sub, Fill)
The PRODIGY R 128 Loudness meters should display each console’s input signal pre PRODIGY processing or filtering
— this ensures the mix engineer’s preset levels match the PRODIGY display
— also, this allows the mix engineer to prove signal levels at any time
A coherent 1 kHz sine wave from both Left and Right outputs at –20 dBFS will register as +3 LU (–20 LUFS)

(ii) Acoustical Alignment, Listening Level

Once sound system optimization is completed, propagation tests should be conducted with appropriate test signals and loudness normalized programme material at a calibrated master output level of 0,0 LU (–23,0 LUFS)
The overall acoustic gain is adjusted to fit local conditions
All loudspeakers should be operational during propagation tests

This procedure differs from R 128 Acoustical Alignment, Listening Level instructions in EBU TECH 3343, pp. 22–23.

In our situation the Reference Listening Level of the loudspeaker system is adjusted to ensure that any A weighted, C weighted, or octave-band Sound Level limits are not breached by programme with a Maximum Loudness Level of 0,0 LU (–23,0 LUFS)

This is found by calibrating the sound system’s acoustic gain (e.g. with propagation tests), and by monitoring the situation throughout.

(iii) Brownian noise test signals

A recommended type of test signal is broadband Brownian noise;
— this has a frequency spectrum that approximates real musical material. [1,p 87, 10,p 3, 28]

Normalized two-minute WAV files are available for download:

https://digbyphonic.com/posts/20250323_LUFS_testsignals/

Tip

Normalized 0,0 LU (–23,0 LUFS) Brownian noise could be included in the default PRODIGY Generators Panel…

(iv) Integrated Loudness (“I”) — Total Time

It is the average, integrated loudness of the whole programme that is normalised. [14,p 7]

The master R 128 meter (i.e. output to PA system) should ‘start’ at the beginning of the event,
and ‘stop’ at the end (Total Time clock).

This indicates the average, integrated loudness of the whole programme.[14,p 41]

Momentary Loudness (abbreviated “M”) — time window: 400 ms
Short-term Loudness (abbreviated “S”) — time window: 3 s
Integrated Loudness (abbreviated “I”) — from ‘start’ to ‘stop’ [14,p 12]

For individual acts (i.e. System 1 console, System 2 console, etc.) the meter should ‘stop’ at the end of each act, ‘start’ at the line-check, and ‘restart’ at the beginning of their performance.

The engineer may find it necessary to restart the “I” meter during the set;
— if so, this should be done during a break in audio.

(v) Mixing the show

Sound mixers should refer to their R 128 meter and listen to the result.

Programme that does not exceed the Loudness Unit Ceiling of 0 LU (–23 LUFS) will likely not exceed the L_p_, Aeq, T upper limit:
— provided the calibration has been completed correctly, and circumstances have not changed.

Remember: for our purpose the R128 terminology of Target Level is transformed into a Loudness Unit Ceiling;
in part, this is to explicitly avoid the trap of continuous operation at maximum levels by default!

Loudness Unit Ceiling

0,0 LU (–23,0 LUFS)

For live programmes the accepted tolerance is ±1,0 LU at –23,0 LUFS

The Programme Loudness Level may be normalized to a Loudness Unit Ceiling lower than 0,0 LU (–23,0 LUFS) on purpose.[25,p 3]

Short-form content

Short-form content

“A programme of short duration (typically shorter than 30 seconds but up to approximately 2 minutes). In addition to advertisements (commercials) and promotional items, interstitials, stingers, bumpers and similar very short items also belong to this category.”[26,p 4]

**Summary: Loudness Parameters for Short-form Content (adverts; promos, etc.):**
Programme Loudness	–23,0 LUFS
Maximum Short-term Loudness (S)	–18,0 LUFS (±5,0 LU on the relative scale)
Maximum True Peak Level	–1 dBTP
Loudness Range	(not applicable)

Opportunity

A change in culture surrounding hearing health is underway.

There is an opportunity to actively encourage an awareness and responsibility within individuals for the hearing of their future selves.

This fair loudness-based measurement protocol is ideally suited to any event that wishes to follow safe listening guidelines†:

providing consistent and predictable loudness and contrast across all program segments.
with noticeable improvements in sound quality, impact, and the audience experience.

Tip

Ensuring that a headline act can play “louder” is straightforward and assured when using the loudness-based approach. [1,p 20]

Make Listening Safe

An upper limit of:

100 dB L_p_{, Aeq,15 min}

This is a feature of the World Health Organization’s 2022
Global Standard for Safe Listening Venues & Events. [1,p 9]

Note

The fair loudness-based measurement protocol can be used for easy integration of the WHO Standard.

Case Study

A number of case studies are planned for 2026.

Please click on the URL link below if you are interested in participating in the research, and furthering the knowledge.

Webpage instructions for the case study:

https://digbyphonic.com/research/rs2024/Loudness_Metering_Live_Events_Case_Study.html

Data from showcase events or anonymous case studies may contribute to the ‘work in progress’ updates of these publications:

Technical Document AESTD1007.1.20-05 : Understanding and Managing Sound Exposure and Noise Pollution at Outdoor Events, 2020. [29]

WHO Global Standard for Safe Listening Venues & Events, 2022. [1]

Conclusion

If there’s to be a competition,
let it be a competition of quality
and not sound pressure level.

It isn’t necessarily the case that higher SPL equates to greater loudness, and vice versa.

The main benefit for stakeholders is parity of loudness across all show elements and acts – using a fairer, psychoacoustically correct measure.

It’ll be useful to calibrate an electrical signal to L_p_, Aeq, T , but what may be more beneficial is the improvement in sound quality.

Dr Bruce Wiggins PhD FHEA MAES PGCHE

Useful Links

Research Paper

J. J. Digby and A. J. Hill, Enhanced Sound Level Monitoring at Live Events by Measuring Audio Program Loudness, in Reproduced Sound 2024, Bristol, GBR: Institute of Acoustics, 2024. [Online]. [10]

Instructions for Mix and System Engineers

https://digbyphonic.com/PGRpres/20250323FairLoudnessSetup/20250323FairLoudnessSetup.html

Presentation for Stakeholders

https://digbyphonic.com/PGRpres/20250323FairLoudnessSetup/20250511FairLoudnessProposal.html

Loudness-to-Dialogue Ratio

European Broadcasting Union, R 128 S4: Loudness Normalisation of Cinematic Content, (2023). [30]

References

[1]

WHO Global Standard for Safe Listening Venues & Events. 2022 [accessed 2026 Jan 30]. https://iris.who.int/bitstream/handle/10665/352277/9789240043114-eng.pdf?sequence=1

[2]

Fastl H, Zwicker E. Psychoacoustics - Facts and Models. 3rd ed. Heidelberg: Springer Berlin; 2007. (Springer Series in Information Sciences). https://www.springer.com/gp/book/9783540231592

[3]

Kuttruff H. Room Acoustics. 5th ed. London & New York: Spon Press/Taylor & Francis; 2009.

[4]

Schneider A. Perception of Timbre and Sound Color. In: Springer Handbook of Systematic Musicology. Berlin, Heidelberg: Springer Berlin Heidelberg; 2018. p. 687--726. (Springer Handbooks). http://link.springer.com/10.1007/978-3-662-55004-5

[5]

White GD, Louie GJ. The Audio Dictionary. 3rd ed., rev. and expanded. Seattle: University of Washington Press; 2005.

[6]

Ginsberg JH. Acoustics-A Textbook for Engineers and Physicists: Volume I: Fundamentals. Cham: Springer; 2018. (SpringerLink Bücher). doi:10.1007/978-3-319-56844-7

[7]

Acoustical Society of America. ASA/ANSI Standard Acoustical & Bioacoustical Terminology Database. Welcome to ASA Standards. 2023 Nov 5 [accessed 2026 Mar 1]. https://asastandards.org/working-groups-home/working-groups-portal/asa-standard-term-database/

[8]

Gallagher M. The Music Tech Dictionary: A Glossary of Audio-Related Terms and Technologies. Boston, MA: Course Technology; 2009.

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Ziemer T. Sound Terminology in Sonification. Journal of the Audio Engineering Society. 2024 [accessed 2024 May 24];72(5):274–289. https://www.aes.org/e-lib/browse.cfm?elib=22419. doi:10.17743/jaes.2022.0133

[10]

Digby JJ, Hill AJ. Enhanced Sound Level Monitoring at Live Events by Measuring Audio Program Loudness. In: Reproduced Sound 2024. Vol. 46. Bristol, GBR: Institute of Acoustics; 2024. https://digbyphonic.com/research/rs2024/Digby_and_Hill-2024-Enhanced_Sound_Level_Monitoring_at_Live_Events_by_Measuring_Audio_Program_Loudness.html

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International Organization for Standardization. ISO 532-3:2023 Acoustics — Methods for calculating loudness - Part 3: Moore-Glasberg-Schlittenlacher method. 2023.

[13]

Moore BCJ, Jervis M, Harries L, Schlittenlacher J. Testing and refining a loudness model for time-varying sounds incorporating binaural inhibition. The Journal of the Acoustical Society of America. 2018 [accessed 2025 Mar 22];143(3):1504–1513. https://doi.org/10.1121/1.5027246. doi:10.1121/1.5027246

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Fiumicelli D, Parker V, Lawrence E, Stewart J. Low Frequency Sound at Outdoor Concerts – a Necessary Noise. Vol. 46. Manchester, UK: Institute of Acoustics; 2024. (2). https://www.ioa.org.uk/catalogue/paper/low-frequency-sound-outdoor-concerts-%E2%80%93-necessary-noise. doi:10.25144/23652

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International Telecommunication Union. Recommendation ITU-R BS.1770-5 (11/2023) Algorithms to measure audio programme loudness and true-peak audio level. 2023 [accessed 2026 Jan 30]. https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-5-202311-I!!PDF-E.pdf

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European Broadcasting Union. Tech 3341-2023 Loudness Metering: “EBU Mode” Metering to Supplement EBU R 128 Loudness Normalization. Geneva: EBU; 2023. https://tech.ebu.ch/files/live/sites/tech/files/shared/tech/tech3341.pdf

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[24]

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[25]

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[26]

European Broadcasting Union. R 128 s1: Loudness Parameters for Short-Form Content (Adverts, Promos, etc.). 2020 [accessed 2026 Jan 30]. https://tech.ebu.ch/docs/r/r128s1.pdf

[27]

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[28]

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[30]

European Broadcasting Union. R 128 S4: Loudness Normalisation of Cinematic Content. 2023 [accessed 2026 Jan 30]. https://tech.ebu.ch/files/live/sites/tech/files/shared/r/r128s4.pdf

Improved Management of PA System Leq Limits and Off-Site Annoyance

Context

Complication

Figure A3.1 [1,p 76]

Loudness \(\not\equiv\) Sound Pressure Level (SPL)

Kuttruff on Sound Pressure Level Meters

Loudness \(\neq\) Volume \(\neq\) SPL/Amplitude/Gain

Solution

Features

The EBU R 128 Loudness Meter

Strategic use of EBU R 128 loudness metering

PRODIGY — the all-in-one solution

Preparation

PRODIGY: Recommended Settings

Example Screenshot

(i) Electrical Alignment Signal and Level

(ii) Acoustical Alignment, Listening Level

(iii) Brownian noise test signals

(iv) Integrated Loudness (“I”) — Total Time

(v) Mixing the show

Short-form content

Opportunity

Make Listening Safe

Case Study

Conclusion

Useful Links

References

Improved Management of PA System
L_eq Limits and Off-Site Annoyance