Low-frequency sound propagation in porous media: glass spheres and pea gravel

White, Michael J.; Swenson, George W. Jr.; Borrowman, Todd A.; Borth, Jeffrey D.

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https://hdl.handle.net/2142/27689 Copy

Description

Title

Low-frequency sound propagation in porous media: glass spheres and pea gravel

Author(s)

• White, Michael J.
• Swenson, George W. Jr.
• Borrowman, Todd A.
• Borth, Jeffrey D.

Issue Date

2011-10-04

Keyword(s)

• low-frequency sound propagation
• sound propagation in porous media
• porous media
• pea gravel
• glass spheres
• characteristic impedance
• attenuation
• phase velocity

Abstract

The sound propagation properties of two air-filled granular materials: large sifted pea gravel and 10 mm diameter glass spheres have been measured in an impedance tube. The experimental method was essentially the same as reported earlier [Swenson et al., “Low-frequency sound wave parameter measurement in gravels,” Appl. Acoust. 71, 45-51 (2010)] for two other kinds of gravel: crushed limestone and undifferentiated pea gravel. Additional sampling and processing steps were applied to the microphone signals such that instead of tones, band-limited random noise was used as the input signal, and spectral domain complex pressures are now offered as input to the estimation algorithm. The estimation process extracts the best-fit attenuation coefficient, phase velocity, and characteristic impedance for the material over the signal frequencies, all with better precision than we previously obtained. Quadratic approximations for the acoustical parameters are given over the frequency range 25-160 Hz. The media are both slightly attenuating and dispersive, having attenuation coefficients within (0.13-0.34 Np/m), phase velocities smaller than those in air (180-240 m/s), and characteristic impedance approximately 3-5 times that for air. Pea gravel was more attenuating, and had slightly higher characteristic impedance, but lower phase velocities than the glass spheres.

Series/Report Name or Number

UILU-ENG-2011-2511

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/27689

Sponsor(s)/Grant Number(s)

Supported by the US Army Construction Engineering Research Laboratory of the US Army Engineering Research and Development Center under the Great Rivers Cooperative Ecosystems Studies Unit agreement, number W9132T-09-2-0008, with the University of Illinois at Urbana-Champaign.

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