Vehicle Approach Notification Device Speed Signal
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Solution Overview
Problem
Silent electric and hybrid vehicles at low speeds are not easily noticeable to pedestrians due to lack of sound, necessitating a vehicle approach notification device that can effectively convey speed information while maintaining sound pressure balance and frequency harmony.
Innovation Solution
A vehicle approach notification device generates a synthetic sound signal with frequency components shifted in specific ranges to maintain sound pressure variation and frequency balance, using a control unit, low pass filter, power amplifier, and speaker to produce a pseudo engine or motor sound, shifting frequency components within a flat frequency range to convey speed without disrupting sound pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If frequency components are shifted according to vehicle speed to notify pedestrians of speed, then speed notification capability is improved, but sound pressure variation increases and frequency balance is disrupted
Solution Approach 1:
The frequency spectrum is segmented into multiple frequency components, each handled differently based on its range. First frequency range components remain fixed to maintain sound pressure balance, while second frequency range components are shifted to convey speed information. This segmentation allows simultaneous achievement of speed notification and sound quality maintenance.
Solution Approach 2:
Different quality treatments are applied to different frequency ranges. The first frequency range components are kept stable (not shifted) to preserve sound pressure characteristics, while the second frequency range components are dynamically shifted according to vehicle speed. This local differentiation resolves the contradiction between information transmission and quality maintenance.
2Loss of information
If all frequency components are shifted to convey speed information, then speed recognition is improved, but notification sound becomes perceived as noise due to sound pressure variation
Solution Approach 1:
The frequency spectrum is divided into first and second frequency ranges. Only the second frequency range components are shifted according to vehicle speed, while the first frequency range components remain unchanged. This selective segmentation ensures speed information is conveyed without causing excessive sound pressure variation that would make the notification sound perceived as noise.
Data Source
AI summary
In a vehicle approach notification device for notifying approach of a vehicle by emitting a notification sound according to a synthetic sound signal composed of a plurality of frequency components from a speaker, a vehicle speed specifying portion specifies a speed of the vehicle, and a synthetic sound signal generating portion generates the synthetic sound signal. The synthetic sound signal generating portion generates the synthetic sound signal such that the frequency component that belongs to a second frequency range in which a variation in sound pressure outputted from the speaker is equal to or smaller than a predetermined magnitude is shifted according to a change in the speed of the vehicle, without shifting the frequency component that belongs to a first frequency range in which the variation in sound pressure outputted from the speaker is greater than the predetermined magnitude.