As I mentioned in my last post, with this generation of ThinkPad notebooks, we've significantly improved both our thermals and our acoustics, meaning our systems run both cooler AND quieter than ever before. Usually these have an inverse relationship -- you can make a system run quieter, but it will definitely feel hotter to the user. Or, you can make it run cooler, but runs into the danger of making it sound like a blow torch. To do both is a pretty amazing engineering feat. Did you know that there are vendors that have warning labels on the bottom of their systems? When I mention my competition by name, I tend to ruffle feathers (pun intended), but if you are a non-Lenovo notebook user, turn your system over. Does it have a warning sticker that says "don't use it on your lap?" Does it have thin felt pads underneath? These are both warning signs that you have a hot running machine. We want our notebooks to run cooler for several reasons. Of course, we don't want complaints, but another reason is that we are simply users of our own technology and we want the best user experience possible. This is especially true when you are crammed into a middle coach airline seat with the person in front reclined, the fat sweaty guy to the right and the arm rest-stealing, Blackberry user to your left. Making these systems cooler required several steps. The first was the easiest. We added more air vents to the bottom of the system. By the principle of insulation by airflow, the air flowing through the system conducts some of the heat from the components before it transfers to the system case. It also serves to cool the components that are already warm. The second step was more difficult. It required redesigning the cooling fan blades as well as their housings. There are five main causes of acoustic noise inside a system: mechanical noise, turbulent airflow rush into the fan, fan blade noise, fan housing noise, and electrical component noise (the hum you sometimes hear). A traditional fan blade used in notebooks has a leading edge that is more or less flat. This shape is found on many bird feathers, such as the Goldeneye pictured below. The feather shape allows the bird to move quickly with a good deal of control while in flight. On a notebook fan this shape moves air efficiently and has the advantage that it is inexpensive to produce. The one main disadvantage of the traditional design is that it is rather noisy, especially at higher RPMs. The turbulence of the airflow is the main cause of this.
Here is what a standard fan blade looks like. In addition to the shape of the blades, the bump on the intake also increases noise.
True story...One of our engineers from Yamato was watching one evening as an owl flew by. He noticed that he saw the owl, but did not hear it. An owl is virtually silent in flight. The evolutionary advantage is that it can swoop down to catch prey without alerting them to its presence. What allows this magic is that an owl has a notched shape to its feathers. The air that flows over its wings makes much less noise than with any other feather design. The engineer studied the shape of the owl's wing and used it to design a fan blade with notched leading edges. These redesigned fan blades are now starting to be used in our latest generation of ThinkPad notebooks. Oh, and no owls were harmed in the making of these notebooks :)
As a side note, you may wonder why all birds haven't evolved to use this feather shape. What the owl gains in silence, it loses in overall speed. It also requires more energy to fly than an average bird. Saving energy is also why the owl can turn its head completely around. It can look for prey in 360 degrees without having to move its body.