Abstract
We apply the method of `acoustic imaging' (Chang et al. 1997) to construct subsurface acoustic images of solar active regions using p-mode signals in different frequency ranges with TON data. Acoustic imaging, based on a time-distance relationship, coherently collects observed acoustic signals at the surface to reconstruct acoustic signals in the solar interior. Earlier studies (Chang et al. 1997; Chen et al. 1998; Chou et al. 1998) have shown that this method successfully reveals acoustic signatures of solar magnetic regions, both in the sense of intensity and phase shift. We now first separate observed p-mode signals into frequency ranges centered at 3, 4, 5, and 6 mHz with a band width of 1 mHz, and use them separately to construct subsurface acoustic images. We will present results of this study to discuss the wave-property effect on the depth resolution in the method of acoustic imaging and to investigate the p-mode frequency and wavelength dependence of acoustic absorption and phase-shift in active regions.