Wave modulation and wave sources in the solar convection zone

We investigate the behavior of upward running sound waves in the lower photosphere by means of a 2-hour time series of FPI-filtergrams and a corresponding series of whitelight images. From the FPI-filtergrams we obtain velocities in two heights in the solar photosphere. Using specific filters in the kh-ν-space, we extract running sound waves from the velocity time series and the granulation from the white-light series. The relation between granular structure and wave amplitude is examined. To this end the granulation images are subdivided into intensity classes. The amplitudes of the waves are extracted on the pixel maps corresponding to these classes. We find hints for wave modulation due to the inhomogeneities in the solar convection zone: The behavior of the wave amplitudes meets theoretical predictions with respect to frequencyand heightdependence. The dependence on the horizontal wave number meets the predictions too, but due to low wave coherence at high wave numbers no definitive statement is possible. Further the darkest locations in the granulation are preferred by waves of increased amplitudes. There also seems to be a preference for the brightest granular regions. In both cases the behavior of the waves can be well described by subsurface sound sources. This is confirmed by comparison of the data with a simple model of a subsurface sound source.