Qscan is a multi-resolution time-frequency search for statistically significant excess signal energy, equivalent to a matched filter search for sine-Gaussians in whitened data. The resulting clustered triggers indicate a time-frequency tile with excess power, whose significance is converted into a signal to noise ratio (SNR) or a Normalized Energy, for matched filter with sine-Gaussians. Sine-Gaussians are characterized by central time, central frequency and the quality factor Q, the ratio of central frequency to bandwidth. A sample sine-Gaussian wave is shown below here on the left, and a sample time-frequency significant tile map at a fixed value of Q, for a typical binary black hole merger signal can be seen below here on the right. Sine-Gaussian waveforms have the minimum uncertainty area, or Heisenberg box, in the time-frequency plane. Heisenberg box for a significant time-frequency region is the multiplication of the duration and the bandwidth of that region.

For more information the reader is referred to this CQG publication and S. Chatterji's MIT thesis.