Noise Guard
With the SpinPoint V10200 Series's revolutionary NoiseGuard™Â technology, SAMSUNG has introduced a new wave of quite PC operation. All SAMSUNG-created hard drives are equipped with NoiseGuard™Â technology, making them the quietest drives in the world. We are currently in the process of designing a "noiseless" drive motor, the FDB (Fluid Dynamic Motor). This paper will explain why HDD noise is a problem and will also showcase the results of our NoiseGuardTM technology.
Over the past decade, Hard Disk Drives (HDD) technology has developed dramatically, especially in the areas of density capacity, and data processing speed. HDD customers chose products based on their processing capacity, price, and reliability. Unfortunately, as HDDs have become more sophisticated, they have also become significantly noisier.
- Technology-savvy consumers are now more sensitive to HDD noise. Major sources of acoustic noise are: A PCs cooling fan and HDD. The average acoustic noise (in sound power level) generated: Cooling fan: 3.4 bels; HDD in normal operation: 3.0-4.0 bels The typical acoustic noise levels at home or in the office is approximately 4.0-5.0 bels Computer generated noise not only distract users, but can also lower productivity levels.
- New PC applications require quieter operation. The advent of the Internet has made the PC part of our everyday lifestyle, a necessity in not only in the office, but in the home as well. At home, PCs tend to be used more for entertainment and Audio/Video applications. PC generated noise interferes with the users ability to watch a DVD or listen to a music file.
- Recent developments in HDDs have made them more powerful than ever. Even the most affordable HDD offer a variety of applications: Opportunities for mass digital storage for consumer devices-TVs, set-top-boxes, digital video recorders, movies, MP3 music, computer games and much more As HDDs have become more advanced, they have also become excessively noisy. Computer generated noise interferes with the consumers audio/video experience. Also, as many computers are located in bedrooms, the acoustic noise created while downloading at night may disturb a good night's sleep.
In the past, noise was measured by means of sound pressure. This antiquated method measured the amount of sound directly above the HDD. This method, however, had its shortcomings, largely because the sound generated on the other sides of the HDD was not taken into account. Currently, SAMSUNG uses the sound power level as an acoustic-noise measuring method, which is measured from all directions using 10 microphones. Figure 1 shows how sound power is measured. A full-radiation plate is installed on the floor to make sure that all sound levels are detected.
Fig. 1. Hemispheric Sound Power Measurement Set-Up in a Semi-Anechoic Chamber of SISA (SAMSUNG Information Systems America), San Jose, California
A typical human ear can detect sounds between 20Hz-20KHz. Among all the audible frequencies, the human ear is most sensitive to sounds in the 1KHz-3KHz range. The quality of sound that humans hear varies considerably, depending on whether or not the frequencies have dominant intensities. Frequencies in the 1-3KHz range that have dominant intensities, or most distracting to the human ear. Reducing the noise at those sensitive frequencies, therefore, dramatically improves sound quality, even when the measured intensity of higher frequencies within the total spectrum is the same or greater.
In developing the NoiseGuardTM technology, SAMSUNG researchers were most interested in pinpointing the source of HDD noise and understanding how it was generated. SAMSUNG's first step in creating NoiseGuardTM technology was to analyze a number of distinctive and important frequencies. Frequencies between the 1KHz-3KHz are most problematic. We analyzed the source of each of these frequencies using Sound Intensity Measurements and Operational Deflection Shape technology in order to determine how to best redesign our HDDs.
Most HDD noise is generated from mechanical vibrations of the rotating spindle motor and read/write sensor positioner. During the rotation process, the spindle motor's internal ball-bearings generate a considerable amount of noise. During the positioning process, high frequency magneto-electric interactions, head stack vibrations, and actuator also contribute to HDD acoustic noise.
The vibrations are also transmitted to the HDA (Head-Assembly). When HDA resonance frequencies are similar to the excitation frequencies, vibrations are furtheramplified, worsening overall HDD noise. In reducing HDD noise, controlling or suppressing energy transmission in the HDA structure can be as effective as minimizing the noise sources.
Through acoustic noise intensity distribution analysis, SAMSUNG researchers identified specific noise sources, and set out to fix these problems with NoiseGuardTMÂ technology. After thoroughly analyzing the acoustic noise loss and absorption rate of various materials, the optimal combination of vibration-absorbing materials was selected.
The shape of the HDD cover was also designed to reinforce the overall structure of the most vibration-susceptible areas, further reducing acoustic noise. SAMSUNG's NoiseGuardTMÂ technology incorporates these design improvements and significantly reduces overall acoustic noise levels, especially those that humans are most sensitive to. At SAMSUNG, we strive to provide our customers with products that are as comfortable as they are reliable.
Figure 2 illustrates before and after NoiseGuardTMÂ technology noise comparisons. This study shows that HDDs equipped with NoiseGuardTMÂ technology emit significantly lower levels of noise (human-detectable frequencies-1KHz-3KHz.)
Fig2. Comparison between before and after of NoiseGuardO Implementation
- "Noise Source Identification of Hard Disk Drives Using Sound Intensity and Its Control", S.W. Kang, Y.S. Han, T.Y. Hwang, Y. Son, J.C. Koo, pp. 1540-1548, June, 2000, KSNVE TRANS. (Korean)
- "A Study on the Acoustic Noise Characteristics of Hard Disk Drives Due to the Structural Excitation of Spindle Motors," Y. Son, T.Y. Hwang, S.W. Kang, Y.S. Han, J.C. Koo, pp. 1549-1554, June, 2000, KSNVE TRANS. (Korean)
