Influence of Pore Size on the Acoustic Absorption Properties of Open-Cell AlSi Porous Cylinders

TL;DR

This study shows that larger pores in aluminum-silicon cylinders improve sound absorption at low frequencies, useful for reducing aircraft noise.

Contribution

The novel contribution is demonstrating how pore size in AlSi alloys affects low-frequency sound absorption for aeroacoustic applications.

Findings

Larger pore sizes (1.8–2.25 mm) achieved sound absorption coefficients of 0.93–0.97 at 500–700 Hz.

Open-cell AlSi cylinders show strong low-frequency sound absorption potential for noise mitigation.

Acoustic measurements followed ISO 10534-2:2023 standard using cylindrical samples with controlled pore sizes.

Abstract

Airframe noise generated at wing trailing edges and high-lift devices, such as flaps, remains a major challenge during landing, with significant contributions in the low-frequency band of 500–1500 Hz. While solid surfaces reflect this acoustic energy, metallic porous materials can effectively absorb it through viscous and thermal dissipation within their internal pore structure. To address this, the present study examines the acoustic absorption characteristics of open-cell AlSi porous cylinders featuring controlled pore diameters between 0.3 mm and 2.25 mm. Measurements were conducted in an acoustic impedance tube according to the ISO 10534-2:2023 standard, using six cylindrical samples (28 mm diameter, 70 mm length). Two sets of measurements were performed for each sample (front and rear faces), and the average values were used. The findings indicate that the normal-incidence sound absorption coefficient α rises as pore size increases, reaching 0.93–0.97 at low frequencies of 500–700 Hz for the samples with the largest pores (1.8–2.25 mm). These results indicate that open-cell AlSi alloys offer strong low-frequencies sound absorption, positioning them as promising options for aeroacoustic noise mitigation, including applications such as porous trailing edge and hybrid flap designs.

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