Large fans are inherently noisier than small ones. Thus larger vehicles must often use two small cooling fans to lessen NVH. Halla's innovation - wave fan and sawtooth shroud - reduces noise substantially, allowing the preferable use of one large fan. Their unit draws less power, pulls as much or more air, and is cheaper to produce. First used by Hyundai, Halla's innovation results in a 3.7 db noise reduction, while reducing weight by 1.2 kg and power draw by 70 W in the Sonata.
Underlying the innovation was careful research and experimentation to understand noise production. Halla's engineers embedded highly sensitive pressure sensors in the surface of fans to measure the extremely small variations in pressure across a rotating blade. No one had done this before, and over a year just to find an appropriate sensor. Halla's studies revealed pressure variations no one knew existed that were significant sources of noise, which Halla's wave-shape fan blade eliminated. Similarly, laser doppler airflow measurements of the backpressure-induced leakage around the fan rim led Halla to develop the sawtooth shroud. Tthis is an exemplary use of empirically driven engineering that led to the redesign of fan blade and shroud, components long considered settled art. Using fundamental understanding of a fan's noise production, Halla changed the shape of the blade and shroud to eliminate the source. The result is radically different-looking.
Halla was able to replace the two-fan cooling units previously used on the Hyundai Sonata (and other vehicles) with a single large fan. It is a very noticeable 3.7 db quieter than the two-fan unit it replaced - and 11 db quieter than the comparable-sized module used on some European luxury cars. The resulting NVH advantage allows Halla's customers to have quieter cars while cutting costs.