Clear the Track: EN 15153-2 Railway Horn Standards

Introduction to EN 15153-2

A train traveling at high speed is surprisingly quiet until it is too close. To ensure the safety of track workers and the public at level crossings, an effective audible warning system is non-negotiable. EN 15153-2, titled “Railway applications – External visible and audible warning devices – Part 2: Warning horns,” establishes the acoustic requirements for these critical safety devices.

This standard ensures that a train’s horn is loud enough to be heard over background noise but not so loud that it causes permanent hearing damage to people on platforms. It also mandates specific musical chords to ensure the sound is instantly recognizable as a “Train” and not confused with a truck or factory alarm.

Snippet Definition: What is EN 15153-2?

EN 15153-2 is a European standard specifying the technical and functional requirements for audible warning devices (horns/whistles) on railway rolling stock. It defines the required Sound Pressure Levels (SPL), the spectral composition (frequencies) of the sound, and the testing methods used to verify compliance for interoperability across European networks.

Acoustic Requirements

The standard does not just say “make it loud.” It defines precise acoustic properties to ensure the warning is effective.

1. Sound Pressure Level (SPL)

The volume is measured at a specific distance (typically 5 meters from the front of the train).

• Warning Horn: Must typically produce between 101 dBA and 120 dBA.
• Soft Tone: Some trains require a lower volume setting for use in stations or depots to reduce noise pollution.

2. Frequency and Chords

To be distinct, railway horns often sound two notes simultaneously (a chord) or separately. EN 15153-2 specifies the allowable fundamental frequencies:

• Low Note: Typically between 311 Hz and 415 Hz.
• High Note: Typically between 622 Hz and 780 Hz.
• The combination creates the dissonant, urgent sound characteristic of European trains.

Comparison: EN 15153-2 vs. UIC 644

Before the EN standard became harmonized law under the TSI, the UIC leaflet was the reference.

Testing Protocols

Compliance is verified through rigorous type testing, either in an open field (free field) or an anechoic chamber to avoid reflections.

• Microphone Positioning: The microphone is placed at the height of a typical human ear (between 1.2m and 1.6m above rail level).
• Background Noise: The ambient noise during the test must be at least 10 dB lower than the horn’s sound to ensure accuracy.
• Durability: The horn mechanism (pneumatic or electric) must withstand millions of activation cycles.

Operational Integration

EN 15153-2 also dictates how the driver uses the horn. The control system must allow the driver to trigger distinct “High” and “Low” notes or a combined chord. In modern trains, this is often integrated into the TCMS (Train Control and Management System) to record every time the horn is sounded for incident investigation.