Liverpool Street Station

Background

Liverpool Street Station is one of London’s busiest interchanges, operating continuously while critical civil engineering and platform improvement works were carried out in 2022.

The challenge was to complete intrusive structural modifications – including core drilling, saw-cutting, breakout of concrete and excavation – while maintaining safe and intelligible public address and voice alarm (PAVA) announcements on active platforms 1-6.

Network Rail’s operational standards require that passenger information and emergency announcements remain clearly intelligible at all times, even under abnormal acoustic conditions. Compliance with these requirements was central to the Noise Management Plan we developed for the project.

What We Did

We were commissioned by J Murphy & Sons to provide a complete acoustic management package covering assessment, planning, monitoring and validation of construction noise impacts on announcement intelligibility.

Baseline and Speech Intelligibility Assessment

• Conducted ambient and PAVA announcement measurements on the platforms to establish existing sound pressure levels and spectral profiles, focusing on the critical 500 Hz – 4 kHz octave bands that determine speech clarity;
• Compared measured data with predicted construction noise spectra to calculate signal-to-noise ratios (SNRs) and identify thresholds for acceptable intelligibility;
• Produced an Assessment of Construction Noise on Speech Intelligibility report for submission to the station operator and Network Rail.

Source Noise Surveys and Modelling

• Undertook pre-works source noise surveys at Kilnbridge yard to measure actual sound power levels of key plant items and tools under controlled conditions;
• Used this data within BS 5228-1-compliant models to predict construction noise propagation across the station concourse and platforms;
• Model outputs directly informed the Noise Management Plan, ensuring predicted levels stayed below the point where the SNR would compromise speech intelligibility.

Noise Management Plan

Developed a bespoke Noise Management Plan (NMP) that embedded:

• Defined noise limits derived from intelligibility modelling;
• Sequencing of high-impact tasks during lower passenger occupancy;
• Real-time coordination between site supervisors and station control;
• Temporary acoustic screening and selection of quieter alternative methods.

The NMP also specified procedures for communicating with the station operator if real-time monitoring indicated intelligibility degradation, aligning with Network Rail’s PAVA performance requirements.

Attended and Real-Time Monitoring

• Conducted attended platform monitoring over successive weekends (May – June 2022) during day and night possessions, recording both quantitative levels (LAeq,T, LAFmax, LA90) and subjective intelligibility ratings;
• Observed security and operational announcements under varying construction conditions, comparing measured SNRs against the established intelligibility baseline;
• Results demonstrated that, while background noise increased during heavy breakout, intelligibility remained moderate to good, validating the effectiveness of the NMP controls.

Stakeholder Liaison and Reporting

• Provided clear, standards-based evidence for the client’s submissions to Network Rail’s operational assurance team;
• Delivered concise summary reports after each monitoring period, demonstrating ongoing compliance with the station operator’s intelligibility criteria and the Control of Noise at Work Regulations.

Outcome

• Maintained intelligibility: All monitored PAVA messages remained intelligible within the required operational range;
• Operational assurance: Network Rail accepted the acoustic evidence as demonstrating compliance with passenger safety and communication standards;
• Data-driven control: Real-time monitoring and predictive modelling allowed adaptive scheduling and avoidance of exceedances;
• Successful completion: Construction completed with zero reported communication incidents or noise-related complaints.

Why It Matters

For major live rail environments, intelligibility of safety announcements is a non-negotiable operational requirement. Our integrated approach – combining source measurement, intelligibility modelling, management planning and verification monitoring – provided tangible assurance that the works could proceed safely, efficiently and in full regulatory compliance.

Project Progress 

Works were completed January 2023.