Eric Baugh

Diminishing returns?: revisiting perception of computing performance

The computing performance literature offers guidelines and frameworks, but data on the limits of user appreciation for performance are scarce. This paper presents a study of user satisfaction with different levels of computing performance. Thirty-five participants performed common computing tasks such as creating email and Web surfing. They rated computing performance for specific task elements - such as application launching and menu responsiveness - that occurred during those tasks. They repeated the tasks under varying levels of computer performance. Results include user ratings as a function of computing performance for each of the task elements. The results have implications for system designers who create products that must meet user expectations for performance.

Designing Notebook Computers to Ensure a Comfortable User Experience: Effects of Surface Temperature, Material, Locality, and Ambient Temperature

Two studies are described to determine the effect of locality, age, gender, ambient temperature, surface material and surface temperature, on user annoyance during a typing task on notebook computers. The studies were conducted in Oregon and Taiwan, using real computers modified with heaters under the keyboard and palm rests. Computer chassis made from both metal and plastic were studied, and users were exposed to ambient temperatures of both 23 °C and 35 °C. No practically significant effect of locality, age, gender, or ambient temperature was observed, but the ergonomic comfort between metal and plastic surfaces was very different at the same temperature.

Applications of psychoacoustics to information technology products

Emerging usage models for computing devices require low acoustic noise, for example in home entertainment systems. Studies have shown that not only the overall level, but also the psychoacoustic aspects matter. This paper provides an overview of testing techniques that are used in the information technology industry and outlines two specific case studies. First, an extensive subjective psychoacoustic study was designed and conducted in multiple geographies to determine the aspects of sound that best describe the annoyance to sound from information technology products in a home type environment. Over 200 participants in four countries participated in this carefully controlled experiment and rated typical steady state sounds on a 5 point annoyance scale. The relevant sound quality metrics were extracted and geographical variations quantified. Second, in a paired comparison study the influence of modulation on annoyance was investigated by superimposing different frequency and amplitude modulated sounds onto a baseline sound. The results indicate that modulation can have a significant effect on subjective perception.

Acoustic Limitations in Notebook Thermal Design

The fan is responsible for the majority of platform cooling in all but the lowest power notebook computers, and is also a major noise source. Fan performance is acoustically limited, and sufficient airflow must be provided within some acoustic target. Data from fan vendors is inadequate for designing a notebook thermal solution since it reflects neither the degradation in performance due to inlet restriction nor the associated noise increase which occurs when installed in the system. Constant sound power, or iso-acoustic, fan curves can be used to properly size the thermal solution, and are shown to correspond to actual system sound power levels. Operator position sound pressure as a function of flow for several systems indicates a wide range of performance among designs, and it is recommended that system impedance be kept as low as possible to maximize flow at a given noise limit.

Overview of notebook fan noise reduction efforts.

Notebook computers face particular challenges with regard to cooling the interior components and the surface of the chassis that is in contact with users, in addition to being operated in a wide range of thermal and acoustic ambient conditions. Fan airflow is responsible for about 85% of the cooling capability in typical designs, and is in turn limited by acoustic considerations. This paper will review fan‐level and system‐level efforts by Intel Corporation to promote low noise fan and system designs. Test fixturing to emulate the restricted space inside a notebook computer, combined with an ISO 10302 plenum, can be used to generate constant sound power fan curves, which capture multiple aspects of fan performance. It can be shown that the optimum design is different for the installed condition than for the free space condition where noise is typically reported today. At the system level, the chassis impedance is intimately connected to the airflow at a chosen noise limit. The location of the fan exhaust ...

Ecma International Acoustic Standard Activities: An enabler for controlling information technology noise emissions.

Ecma International is an organization that facilitates the timely creation of a wide range of standards for Information Technology (IT) products, including acoustics standards. Ecma standards have a history of short development time and revision. Each Ecma acoustics standard will be discussed demonstrating how it promotes the analysis and control of IT product noise. ECMA‐74 is the test code for sound emissions from IT equipment. Annex C includes uniform operation and installation conditions for most types of IT equipment and is now referenced by the latest versions of ISO 7779:2010 and ANSI S12.10. This reference by other standards ensures that there is a world‐wide consistency on mounting and operating conditions and that these procedures are up to date. The latest edition of ECMA‐109 on noise declarations for customers presents revised guidelines to manufacturers on making declarations when testing a small sample size. ECMA‐108 presents methods for determining high frequency sound power and has been su...

A relation between flow, noise, and system impedance for notebook computers.

Performance of notebook computers is strongly limited by the ability to reject heat from the system. In a typical mainstream design, the airflow driven by the internal fan is responsible for about 80% of the maximum cooling capability, and this airflow impacts all the internal components (CPU, memory, radios, etc.) as well as the top and bottom skin temperatures. Fan flow, in turn, is limited by acoustics. It has been shown that the fan installation conditions inside a notebook computer have an adverse effect on both flow rate and noise. The market trend is toward thinner systems, which generally have a higher system impedance. As impedance increases, system airflow must decrease to maintain a fixed acoustic limit, holding all other variables constant. In order to demonstrate the effect of impedance, this paper describes a simple, two parameter model relating the flow rate in a notebook computer at a given operator position sound pressure level to the impedance index of the system. This relation is shown ...