The broadband noise from the quasar is recorded at different frequency bands. The 2Gz band (S-band) is used to calculate the atmospheric delay, as it is less prone to this kind of disturbances than the 8Gz band (which is the band we are actually more interested in).
As we are trying to reconstruct a broadband signal, but we only have space (data size) to capture parts of the spectrum, we record different frequency bands that are spread out at inharmonic ratios. If were recording at harmonic ratios, we would capture less new information with each new band (redundancy), so the frequency bands are carefully chosen to be at nonharmonic intervals.
Here are two sounds created by transposing the observation frequencies down into the audible range. In and of thems selves, they sound kind of "outer space-y" to my ears.