Vibration during recording can induce radial variations in track location that are below the 500-10,000 Hz frequency range of radial noise tests. Although radial acceleration tests cover frequencies below 500 Hz, mechanical vibrations could generate high amplitude, low frequency radial displacements having negligible values of radial acceleration. The internal drive chassis is normally attached to the outer case by vibration isolators. These may be tuned for a specific chassis assuming that the outer case is rigidly mounted. Uncorrectable errors observed by Media Sciences are most severe when the drive is unmounted or is in a lightweight external cabinet.
Significant vibration is observed in such cases, especially with high speed drives.
The effect is real, even though the cause has not yet been pinpointed. Types and numbers of uncorrectable errors are closely related to the recording drive, varying between drive manufacturers, models, and individual drives. Rigidly mounting the drive in a heavy enclosure helps but does not fully correct the problem. Certain drives may be satisfactory at 1X or 12X, while others with the same model number and date code may not. Some drives record good discs at lower speeds, such as 2X or 4X, while others do not.