Laser-doppler vibrometer measurements of acoustic to seismic coupling

✍ Scribed by W.Patrick Arnott; James M. Sabatier

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 606 KB
• Volume: 30
• Category: Article
• ISSN: 0003-682X
• DOI: 10.1016/0003-682x(90)90078-9

✦ Synopsis

A n atmospheric sound wave can couple with the poroelastic ground, resulting in ground motion. This is the phenomenon of acoustic to seismic coupling. Previously, ground velocity was measured using geophones. We report vertical ground velocity measurements made with a modified off-the-shelf laser-doppler vibrometer (LD V). The measurements are difficult because high atmospheric sound pressure levels of ~, 100 dB relative to 20 I~PA are necessary for good signal-to-noise in the acoustic-to-seismic coupling ratio measurements; the LD V also couples with the sound field above the ground. We report good agreement among geophone and LD V measurements of vertical ground velocity for an impulsive atmospheric sound source. A continuous wave sound source was used to measure the transfer function of the LD V system for frequencies in the range 100-500 Hz.