Preliminary measurements of sound attenuation by snow over a model seal lair

Abstract

Because of their winter habit of denning in snow above Arctic ice, ringed seals, Phoca hispida, may be exposed to airborne man-made noise. Incidental to acoustical studies of winter seismic exploration [D. V. Holliday et al., J. Acoust. Soc. Am. Suppl. 1, this meeting] a series of measurements was undertaken of airborne tones received in a model seal lair. Five successive layers of snow blocks were added around the sensor. Seven tones from 105 to 10 510 Hz were played from a loudspeaker at two distances, 0.8 and 11.5 m, through the accumulative five layers (maximum thickness, 0.9 m). This study was undertaken off Prudhoe Bay, Alaska, April 1983). The results indicated an increasing transmission loss through the “lair” wall of about 6 dB/doubled thickness, an increasing dependence with frequency (Hz), and evidence of significant propagation through the ground path. It is tentatively concluded that, in this situation, snow may be an effective barrier for higher frequency airborne noise, but attenuation is limited by flanking propagation through the underlying medium. [Work sponsored by NOAAs National Ocean Survey, Office of Oceanography and Marine Services.]