Speed-dependent directivity patterns of road-traffic vehicles.

Area of Science:

• Acoustics and Noise Control
• Vehicle Engineering
• Signal Processing

Background:

• Vehicle exterior noise arises from tire/road, powertrain, and aeroacoustic sources.
• These sources emit sound with distinct, speed-dependent directivity patterns.
• Understanding these patterns is crucial for noise mitigation and vehicle design.

Purpose of the Study:

• To identify spatial and speed-dependent directivity patterns for various road vehicles (electric, hybrid, combustion).
• To analyze spectral properties and speed-dependent sound power.
• To compare findings with the Harmonoise model and provide an open-access dataset.

Main Methods:

• Utilized time-variant wave backpropagation on microphone array signals.
• Analyzed directivity patterns in third-octave bands.
• Compared derived patterns with the analytical Harmonoise model.

Main Results:

• Directivity patterns vary significantly with driving conditions (e.g., engine speed, gear).
• Patterns are more symmetric in the median plane and asymmetric/directional in the sagittal plane.
• Sound power levels vary widely (10-20 dBSWL) at the same speed, converging at higher speeds.

Conclusions:

• Driving conditions, beyond drivetrain type, critically influence vehicle noise directivity.
• The study provides a comprehensive dataset for noise mapping and auralization.
• Findings contribute to better understanding and control of vehicle exterior noise.