FrostyTech posted a Coolermaster Hyper48 KHC-L91 Heatsink Review

The Coolermaster Hyper48's all copper construction is augmented by four copper heatpipes that advance the flow of heat out from the base to the upper tips of the cooling fins. As we will see shortly in the synthetic thermal test results, the heatpipes play an important role. Really though, the most notable benefit of the Coolermaster Hyper48 heatsink is its quietness. The low noise output is due to a specialized Delta fan which has side vents and a conservative impeller speed. The 92x92x25mm Delta NFB0912L fan moves 42CFM of air whilst generating just 29.1 dBA noise, according to the mfgr's spec sheet.

Coolermaster Hyper48 KHC-L91 Heatsink Review