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August 5, 2003 -- by Mike Chin
Optical drives are among the PC components we have been reluctant to examine seriously for acoustic performance. It's not that they don't make noise; optical drives certainly do make a lot of noise. The question is whether any device can run quietly while spinning an intrinsically imbalanced 5" diameter plastic disc at many thousands of RPM. The fact is, noise emitted by an optical drive is most closely related to the speed at which it is spinning the disc. Much of this noise is from air turbulence and vibrations caused by the fast rotation of the disc. Only some of it is mechanical drive and electronic motor noise.
Yet there are distinct differences in noise reported by many listeners, even when the drives are rated for the same read / write speeds. They are all noisy, but some are noisier, and some are quieter. Many regular visitors of SPCR have called for noise-focused reviews of optical drives to add to our database of knowledge about the noise of PC components. Finally, Samsung Canada recently sent over a couple of optical drive samples and requested a review. Our quest, then, is to identify the quieter ones so that an otherwise quiet PC does not have to sound like a vacuum whenever the optical drive is accessed.
Both images on this page courtesy of howstuffworks.com
It will be helpful to have an understanding of how optical drives work. Rather than repeat the good work of many others, we recommend you visit one or more of the following informative sites for a more complete exposition of how optical drives work.
PC Magazine's Flash animation of How Optical Drives Work
How CD Burners Work, a detailed look by howstuffworks.com
CD Player, also by howstuffworks.com
How DVDs and DVD Players Work, also by howstuffworks.com
Here, we are concerned primarily with the noise-producing parts of an optical drive, the parts that move:
- A tracking mechanism moves the laser assembly so that the laser's beam can follow the spiral track (from the innermost point outward). The tracking system has to be able to move the laser at micron resolutions and to position it quickly for random access. This is a typical source of noise.
- A drive motor that spins the disc at precise speeds depending on which portion of the track is being read. This is the main source of noise.
Most optical drives of greater than ~12X read / write speed use constant angular velocity (CAV) or a compromise combination of CAV and constant linear velocity (CLV) to improve transfer rates at the inside edge of the disk. In any case, rotational speeds in excess of 12,000 RPM are not uncommon with ~50X drives in mid-2003. No wonder they are so noisy! (See this explanation of CAV & CLV in The PC Guide web site.)
The noises emitted by an optical drive can be divided into several categories. These are the categories of optical drive noise we will examine:
1) High speed data transfer / write rotational noise. This is usually the maximum level of noise produced by an optical drive. This noise will be measured in dBA @ 1 meter as well as described narratively. Each drive will also be run at a lower-noise reference read setting of 24X speed using CDBremse. This will allow an apples-to-apples comparison of optical drives that operate at different speeds.
DVD players will be measured for noise as well as listened to during normal playback of movies. The same set of CDs and DVDs will be used in doing read noise measurements and listening.
2) Positioning read noise. The noise made by an optical drive upon first insertion of the disc when the summary of the contents are scanned. This noise will be described.
3) Drawer mechanism noise. Some operate smoothly and quietly while others grind loudly. This noise will be described.
4) Rotational vibration. Some discs are less balanced and cause more wobbling and vibrations, which in turn, lead to more noise. The imbalance of discs is random and uncontrollable. However, some drives seem to deal better with imbalanced discs because of clamping / damping mechanisms. This vibration will be described.
Although we use a high precision sound level meter for acoustical analysis, we rely more on subjective listening than on measurements. This is because measured dBA is only one aspect of noisiness, and human perception is the final arbitor.
Each optical drive will be used on the test bench, not mounted in a PC case. This elminates interactive variances that arise with vibrations, resonances, etc. that may only complicate acoustic analysis. Any one of several test systems will be used. They all run Windows XP and share the important characteristic of making very little noise, typically 20 dBA @ 1 meter, so that they do not impinge on the analysis of the noise made by optical drives under test.
NOTE: The read / write performance of the optical drives we review will NOT be examined. Our point of view is simple: Optical drive performance testing is already done by many hardware sites. There is no need to duplicate such efforts. Any good performance testing takes time and effort. Time and resources at SPCR are precious and much better spent expanding our knowledge about the acoustic aspects of optical drives, which is hardly touched by any hardware reviewers. On top of all this, the performance difference between various makes is relatively subtle, and most are plenty fast for most applications; on the other hand, a very quiet optical drive is a gem, a find.
Web sites that provide good performance-oriented reviews of optical drives include:
Let's move on to the reviews...
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