  The Birmingham Solar-Oscillations Network (BiSON) has collected helioseismic
data over three solar cycles. We use these data to determine how the internal
properties of the Sun during this minimum differ from the previous two minima.
The cycle 24 data show oscillatory differences with respect to the other two
sets, indicating relatively localized changes in the solar interior. Analysis
of MDI data from Cycle 23 and Cycle 24 also show significant signs of
differences.
