Fan Speed Modulation for Noise Reduction
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Solution Overview
Problem
Current fan control methods cause noise discomfort for users due to the continuous single pure tone sound produced when rotational speed is switched between modes, leading to a perception of noise as the fan speeds up.
Innovation Solution
A method that adjusts the fan's rotational speed within a range of variation around a second mode value, incorporating fluctuating audio frequencies by modulating the input voltage, breaking the continuous single pure tone sound and creating a characteristic sound with changing frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the rotational speed of the fan is adjusted between different mode values to control heat dissipation, then the heat dissipation rate is improved, but the user perceives noise due to continuous single pure tone sound
Solution Approach 1:
The patent applies periodic action by adjusting the rotational speed of the fan in a periodic fluctuating manner within a specific range around a target speed, rather than maintaining a constant speed. This periodic variation in rotational speed causes periodic variation in the sound frequency, transforming the continuous single pure tone into a fluctuant sound that is less perceptible as noise to users, while still achieving the required heat dissipation rate.
2Productivity
If the fan rotates at high speed to dissipate waste heat effectively, then the heat dissipation performance is improved, but the sound dB and frequency increase making the noise more noticeable
Solution Approach 1:
The patent applies parameter changes by varying the rotational speed parameter within a specific range around the target speed rather than maintaining it at a fixed high value. This parameter variation transforms the sound characteristics from a steady high-frequency pure tone to a fluctuant sound pattern, reducing noise perception while maintaining adequate heat dissipation efficiency through the fluctuant speed variations.
Data Source
AI summary
A method for controlling a fan is provided for adjusting the rotational speed of a fan. The method includes adjusting the rotational speed of the fan from a first mode value to a range of rotational speed variation, wherein the upper bound of the range of rotational speed variation is a second mode value plus a first variation value, and the lower bound of the range of rotational speed variation is the second mode value minus a second variation value; and adjusting the rotational speed of the fan in the range of rotational speed variation during a time period. Thus, a user will not consider the sound from the fan as a noise.