Infrasonic wind-noise reduction by barriers and spatial filters

Area of Science:

• Atmospheric acoustics
• Geophysics
• Environmental monitoring

Background:

• Infrasound arrays are crucial for monitoring global events but are susceptible to wind noise.
• Traditional noise reduction systems, like rosette spatial filters, require significant land area.
• Limited land availability at International Monitoring System (IMS) sites necessitates alternative noise reduction solutions.

Purpose of the Study:

• To experimentally evaluate the effectiveness of a novel wind barrier for reducing infrasonic noise.
• To compare the performance of the wind barrier against rosette spatial filters and a reference site.
• To assess the suitability of the wind barrier for IMS infrasound array sites with land constraints.

Main Methods:

• Experimental observation of wind speed and infrasonic noise reduction within a 2-m-high, 50%-porous hexagonal wind barrier.
• Comparison of barrier performance with rosette spatial filters and a reference site (no noise reduction).
• Analysis of noise reduction effectiveness based on reduced frequency (f*L/v) across different wind speeds.

Main Results:

• The wind barrier reduced wind speed by 90% and infrasonic noise by up to 20-25 dB above a critical reduced frequency.
• Below the critical frequency, the barrier provided a 4 dB reduction, while rosettes showed no reduction.
• Noise reduction data across various wind speeds collapsed into a single curve when plotted against reduced frequency.

Conclusions:

• The investigated wind barrier is a highly effective solution for infrasonic noise reduction at IMS array sites, especially where land is limited.
• The barrier offers superior performance compared to rosette spatial filters, particularly in its ability to capture signals without integration through narrow pipes.
• The findings support the adoption of this wind barrier technology for enhancing the quality of infrasound data acquisition.