Identifying Short Time High Pitch Squeak Noise from Electric Window in Car Door Case Study

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Courtesy of Norsonic AS

Problem

A well known car manufacturer in Korea were testing an automatic car door window intended for one of their new car models. The window is driven by an electric engine positioned in the middle of the car door that drives the window up and down. When the window was driven up by the electric motor, a short timed high pitch squeak noise could be heard as seen from the level versus time plot below. The squeak noise was obviously connected to the window and the car door, but the localisation of the source of the problem proved difficult.

Measurements

The Nor848A-0.4 40 cm camera with 128 microphones was used for the recordings. The camera was positioned at a distance of 2.0 m from the car door, with the front-end of the camera pointed straight at the door. The recording consisted of an event of the car window going up whilst being driven by the electric engine.

Results

In addition to the high pitch squeak noise, sound from the electric engine could also be heard which was around 670 Hz as seen below. Since this sound was present during the entire recording, it could be easy to misinterpret the results and pinpoint the source of the high pitch noise to the wrong location without doing proper analysis. As seen in the image below, the location of the electric engine was in the middle of the door.

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