ISO 16254:2024

Overview

ISO 16254:2024 - Acoustics - Measurement of sound emitted by road vehicles of category M and N at standstill and low speed operation - Engineering method - defines an engineering test method to objectively measure the external sound emitted by road vehicles when stationary or operating at low speed. Derived from ISO 362-1, the standard reproduces the sound levels generated by principal vehicle sound sources relevant to pedestrian safety, and provides procedures for assessing both native vehicle noise and purpose-built external sound generation (ESG) systems.

Key technical topics and requirements

• Scope and purpose: Measurement of sound for category M and N vehicles at standstill and low speed to inform pedestrian detectability and regulatory certification.
• Test environments: Requires an extensive open space (outdoor) acoustic environment for full-vehicle tests; provisions for indoor hemi-anechoic/anechoic testing for components and ESG systems.
• Instrumentation: Specifications for acoustic instruments, speed measurement, and meteorological sensors; includes daily verification and conformity requirements.
• Microphone configuration: Multiple microphone positions and allowance for multiple microphones per location to reduce measurement variability.
• Signal processing and metrics:
  • A-weighted sound pressure levels and one‑third octave band analysis.
  • Frequency shift measurements and tonal identification using spectral analysis.
  • Psychoacoustic tonality (tonal loudness) as an additional metric to quantify audibility and identify the most perceptible components across critical bands.
• Environmental controls: Meteorological condition limits and background noise criteria; flowcharts and procedures for background noise assessment.
• Test procedures and reporting: Detailed procedures for full-vehicle tests (standstill and slow-speed cruise), data compilation, uncertainty analysis, and required test report content.
• Annexes: Informative material on development, frequency identification methods, tonality, and frameworks for measurement uncertainty (referencing GUM).

Practical applications - who uses this standard

• Regulatory authorities for vehicle certification and compliance testing.
• Vehicle manufacturers (OEMs) and suppliers to design, validate and certify ESG systems and to benchmark low-speed/noise emission behavior.
• Vehicle testing stations and independent laboratories conducting production checks or type-approval testing.
• Acoustic consultants and safety engineers evaluating pedestrian detectability, mitigation measures, or product development.
• Accessibility and advocacy groups informing requirements for audible vehicle cues.

Related standards and references

• ISO 362-1 (source basis for methodology)
• ISO/IEC guidelines on measurement uncertainty (GUM) - referenced in Annex D
• Developed in cooperation with SAE vehicle-sound working groups

Keywords: ISO 16254:2024, vehicle sound measurement, acoustics, external sound generation, pedestrian safety, standstill, low speed, tonal loudness, psychoacoustic tonality, A-weighted sound pressure level, certification.