Acoustic emissions from active cooling solutions for portable devices

Due to ever increasing consumer demand, today´s market place is full of portable computing devices such as notebook computers, gaming machines, personal digital assistants (PDA´s) and smart phones. In each of these technologies processing power and functionality levels are continuing to increase resulting in increased thermal management issues. The former of these technologies already use an active cooling solution with a profile of 10 mm to 15 mm whilst the latter two are quickly approaching the limits of passive cooling. Since a common characteristic in each of these technologies is the desire to reduce profile height, there exists a need to develop low profile cooling solutions that are capable of supporting this growing market. However, a prerequisite to developing such solutions is an accurate understanding of how the noise level characteristics of the driving fans scale with profile height. This work experimentally addresses the scaling of low profile fans in terms of acoustics. The rotor heights range from 0.5-15 mm with diameters from 15-32 mm, giving an aspect ratio of height relative to diameter of 0.03-0.6. The results can be used as a foundation for the development of active cooling in mobile devices where both correlations for noise levels and basic design criteria are identified.