Noise Control Enclosure for an Electric Fan Motor

An air circulating fan motor located within the passenger compartment of an automobile was emitting an objectional noise. Both the level and frequency range of the noise contributed to the problem. Although the total Sound Power Level (SPL) at the passenger location was not expected to be reduced, due to the multitude of sources contributing, the goal of the program was to develop a noise control barrier for the motor which would eliminate the contribution of the motor to the total SPL.

The first concern was to verify that a barrier would indeed eliminate the problem. This was accomplished by designing an ideal barrier for the motor. Even though this ideal barrier would not be amenable to a production solution. A nine dB reduction resulted from the ideal barrier and the program continued through the design and evaluation of a field usable barrier.

This paper will present the details of the efforts completed during the development of the enclosure.