Something loud but pleasantly pitched can be more tolerable than something quiet but irritating. “There’s a bit of math behind it, but you can create broadband noise instead of total noise with that technique.”Īpple engineers have to find creative ways to exploit the laws of thermodynamics. In this case: “That borrowed almost entirely from automobile tires,” Ligtenberg says. Noise is a major factor in the design of modern machinery. So you don’t get huge harmonics that tend to be super annoying.” “They’re still dynamically balanced, but they’re actually randomized in terms of their BPF. “Years ago, we started redistributing the blades ,” he says. Since most off-the-shelf fans would be too loud, Apple designs them internally. Ligtenberg’s group built the Pro’s fan system-three axial fans in the front, with a blower in the back. Before that, he had a Piper straight-tail Lance, PA32R-300). “I fly a Beechcraft Turbo Bonanza, B36TC,” he says. His name is on dozens of the company’s patents, but he’s especially interested in how air moves. Among those engineers is Chris Ligtenberg, Senior Director of Product Design.