Line asymmetry of solar p-modes: Properties of acoustic sources
  The observed solar p-mode velocity power spectra are compared with theoretically calculated power spectra over a range of mode degree and frequency. The shape of the theoretical power spectra depends on the depth of acoustic sources responsible for the excitation of p-modes, and also on the multipole nature of the source. We vary the source depth to obtain the best fit to the observed spectra. We find that quadrupole acoustic sources provide a good fit to the observed spectra provided that the sources are located between 700 km and 1050 km below the top of the convection zone. The dipole sources give a good fit for significantly shallower source, with a source-depth of between 120 km and 350 km. The main uncertainty in the determination of depth arises due to poor knowledge of nature of power leakages from modes with adjacent degrees, and the background in the observed spectra. 
Pawan Kumar and Sarbani Basu (IAS, Princeton)