I changed laptops about a month ago. I had a Windows netbook, and I opted up, as it were, to a Macbook Air. Part of the attraction of the Macbook Air was its solid-state drive. Unlike a traditional hard drive, which is in effect a high-tech LP player with read-write capability, the SSD has no moving parts -- well, except at the level of the electrical charge that allows data to be stored. (If you can hear that, please get in touch while the next X-Men movie is still in pre-production.) The lack of a physical interface means the SSD is silent, and also less likely to trigger the computer's fan, which in most cases is the primary producer of computer noise on a laptop or desktop. (Note: You can, indeed, upgrade netbooks to SSD drives, but the one I had, a slim Acer, had its drive buried so deep in the device that it was beyond my abilities and my time.)
Beyond the fan, the main mechanical part of a laptop is its keyboard. The Macbook Air's keyboard is one of the best I've worked with. I've long been skeptical of Apple keyboards, believing that they at times achieve their pronounced elegance, their fiercely minimalist silhouette, at the expense of functionality. The one on the Air, however, is splendid. (Mine is the "2011 Air," so unlike its Air predecessors, the keyboard has the additional benefit of being backlit). I've typed on both my iPad 2 and my Air next to my sleeping 14-month-old, and it's possible that the Air keyboard is the quieter of the two -- perhaps not quantitatively, in terms of measurable amplitude, but almost certainly qualitatively: The finger-tap sound of the iPad screen is akin to cold, hard raindrops. It's a sound is so singular and strong that it can seem even louder than the cushioned noise of the Air's keyboard.
With one prominent exception (the trackpad), the deficits I've come across on the Air, in terms of troubling sonic properties, are restricted to its operating system (OS X Lion), and the very near silence of the SSD may be responsible for bringing them to the foreground. Here are some notes on the three most persistent of those sounds, and on compensating for them:
TRACKING ERROR: The Air's keyboard may be blissfully quiet, but its trackpad is another story. Like the single physical button on the iPad, the trackpad click on the Air emits a peculiarly hard crunch. It's like a small chitinous thing being stepped on. Fortunately for iPad users, the latest major upgrade of its operating system, iOS 5, made that button less necessary than it had been in the past: various swipes accomplish the majority of its tasks. The Macbook Air default setting requires you to click hard on the trackpad to click on anything (like a webpage link, for example). However, there is a setting under "System Preferences" to correct this. Just select "Trackpad," which appears under "Hardware." Then select the "Point & Click" menu. And then click on "Tap to click." In most but not all cases, a simple (and near silent) tap on the trackpad will now accomplish most of the hard-click tasks. By the way, I have noticed a few instances when you still need to click hard, but very few (example: when selecting a user account on the laptop after turning on the machine).
SILENT BOOT: There are several means to disable the "ah-ahhh" sound that the laptop makes when it turns on. You know the one, the choral effect that no doubt will fill the heavens when the Singularity happens, and that in the meanwhile embarrasses laptop wielders on a daily basis in libraries and cafes around the globe. I'm currently using a tiny app called Auto Mute (at auto-mute.com), which I'd previously used in Windows. I believe it initiates itself just in time to beat when the computer triggers the "ah-ahhh." As with the Windows implementation of Auto Mute, I have experienced a few instances when the computer's boot somehow fails to launch the tiny application in time. But for the most part the fix works. There are various other approaches to this problem, enough to suggest that there is widespread displeasure with not being able to turn it off permanently in some official "System Preferences" manner. According to Tech Heavy, you can also hold down the Mute button while the laptop is being turned on, or use a tool called StartupSound.prefPane, which is an alternate to Auto Mute.
SLIDING SCALE: One of the most annoying aspects of OS X is the beeping noise that accompanies the lowering and raising of volume in Lion. A little plinky beep accompanies each move up and down the 16-step scale. As with the Trackpad issue, this can be handled thanks to a little option buried deep in the "System Preferences." Click on "Sound," which is under "Hardware." Click on the "Sound Effects" menu. And then de-select the option that reads "Play feedback when volume is changed." Doing so doesn't turn off the graphic that appears when the volume is raised and lowered: you'll still be able to gauge, visually, where the computer is at on the volume scale.
I have to say that the silence of the SSD, the hushed feedback of the keyboard, and the way the fan is triggered only under the most CPU-intensive circumstances combine to make the Air a pleasure to use. No doubt as a result of that silence, other inherent noises -- in both the hardware and the software -- will turn into annoyances, the personal-technology equivalent of a neighbor who walks too loudly. But for the time being, at least, I have succeeded in muting the most troublesome of them.