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As our society becomes ever-more mobile, our digital devices continue to get smaller. We can listen to our entire musical library on an iPod that weighs less than 5 ounces. The shrinking of our digital devices is also being seen in our computers, as ultra-thin notebooks are no longer the smallest things around. Customers wanting to stay connected without compromising computing power are turning to netbooks.
Netbooks are smaller versions of traditional notebooks, and are attractive to mobile users because of their compact design and low price point while still maintaining the functionality of a notebook. With the success of the ASUS Eee PC netbook, other major OEMs, such as HP, Dell and Lenovo, have followed with their own netbooks.
Consumers are enticed by the portability of netbooks, as well as Ultra-Mobile PCs (UMPCs) and Mobile Internet Devices (MIDs), and use netbooks as their secondary PC or notebook. With that in mind, the size, dimension and weight of the netbook, and its associated components, design and placement, are critical. These restrictions have created a new challenge for designers - how to design a quality audio experience in these tiny devices. As for consumers, they are faced with a new set of issues when it comes to choosing a netbook that meets their audio needs.
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| The Asus Eee PC Netbook |
The main operating systems (OS) used in netbooks are Windows XP and Linux-based OS. These operating systems work best with the low-power CPUs in today's netbooks, which are mostly running Intel Atom processors, and offer the best fit for the system requirements, specifications and configuration of netbooks. Linux enables a lower-cost solution for netbook designers as its royalties are lower, helping keep the price point low. Linux also uses less system memory, which is required for higher performance, and is generally much faster than Windows.
Although Linux may be a perfect fit with regards to many functions of a netbook, it does not provide dynamic audio. Windows quickly became the dominant PC operating system, meaning that since Linux wasn't in high demand for PCs, the audio capabilities of Linux became an afterthought and software enhancements were not readily available.
As Linux does not have built-in high-quality audio capabilities, a software driver with optional advanced technologies must be added to devices running Linux. The driver needs to feature a systemwide equalizer, a compressor/limiter, acoustic echo cancellation and noise suppression. These features will help offset the low-quality speakers that are generally used in these small form factor devices, which is necessary to maintain a reasonable price point.
Small form factor netbooks with low-quality speakers generally produce poor sound or frequency responses from music. To compensate for this problem, an equalizer can set and adjust various bands, filters and frequency width to create a systemwide parametric equalizer, or multi-band equalizer that contours the sound on the PC to improve the audio fidelity and listening experience. The amplitude of each band can be tuned with the shifting and widening or narrowing of the center frequency.
In addition to music, low-quality speakers and poor audio sub-system design in netbooks will also be noticeable when watching a video or movie. For example, when listening to a conversion during a battle scene in war movie, typically the speech between two characters is not as clear or loud because of background war noise. This results in a poor user experience as quiet conversation or media can be difficult to hear while loud voices can become much distorted and might even damage the small, space-constrained speakers. To help with this, an audio compressor and limiter feature allows the system builder to make the system as loud as possible without distorting and damaging the low-cost speakers of the unit. It does this with real-time precision and can make the system more than 5 decibel (dB) louder without turning up the internal amplifier.
A compressor basically reduces the dynamic range of an audio signal into a smaller dynamic range. In the movie example, it reduces the level of the loud explosions, but not the gentle sounds of the conversation between two characters. Thus, the level can be raised where the conversation can be heard without the loud sounds being too loud. This is also very similar to an automatic volume control in an automobile.
A limiter or limiting is similar to compression, but it is used to make sure that the audio signal does not go above a specified level. This is extremely helpful to prevent the low-quality speakers and amplifiers from overloading or even being destroyed by excessive power peaks, and ensures that users don't experience distortion. When purchasing a netbook from a retailer, the consumer should look for words like "speaker protection" or "audio normalization." These are two common names for a limiter. The compressor and limiter will come pre-installed on the system, and will protect the complete audio system.
Another main feature of the netbook is wireless LAN for Internet connectivity. Many people are using netbooks as an Instant Messaging (IM) and video portal to stay in touch with friends and family. However, with noisy environment and feedback from the internal speakers and microphones, the Voice over Internet Protocol (VoIP) or chat experience is not pleasant because the sound from the speakers is picked up by the microphones.
Acoustic Echo Cancellation (AEC) and Noise Suppression (NS) technology can help provide a better VoIP experience. These features provide enhancement to built-in and external microphones so VoIP-type and other voice applications will have enhancements to block out noise and sounds that come from the PC itself.
AEC is a vital feature for any type of real-time communications (RTC) device that does not use a close-talking microphone in a headset to isolate and separate the speakers and microphones. It synchronizes the output signal and input signal so the speaker signals can be subtracted from the microphone signal, thus reducing any sounds from the speakers that are picked up by the microphones.
NS, which is also called noise reduction or noise cancellation, helps eliminate the noise in a speech signal to make the speech more clear. Typically, this is done by a bandpass filter tuned to match the range of human speech, thus reducing any noises between spoken words.
When shopping for a netbook, look for terms like "speech enhancement" or "echo cancellation" on the features list. These types of features will be pre-installed on the system so the user does not have to buy a third- party application.
Netbook users will have a better audio experience with these features included in their Linux-based OS systems. From listening to music to watching streaming movies to chatting with family to protecting the speakers from damage, netbooks need features, such as an equalizer, compressor, limiter, AEC and NS, to improve the audio quality and experience.
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Steven Tellman is a Product Manager in the Computing and Multimedia Division of Integrated Device Technology (IDT). He is also the Manager of PC Audio Linux support and development within IDT. Henry Wong has more than 11 years of marketing and engineering experience in the semiconductor industry worldwide. Prior to IDT, Henry held various key roles at SMSC, Qimonda, Infineon Technologies, Philips, and have received patents at Intel Corporation and Nortel.
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