Vehicle Sound Apparatus Using Comb Filter for Pedestrian Recognition
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Solution Overview
Problem
Low-noise vehicles, such as electric and hybrid vehicles, pose a risk to pedestrians due to their reduced audible approach noise, and existing solutions using high-frequency dummy sounds fail to effectively convey the vehicle's approach, as they lack low-frequency components and are easily attenuated, making it difficult for pedestrians to recognize the vehicle's presence.
Innovation Solution
A sound producing apparatus that utilizes a comb filter function to amplify specific frequency components of the vehicle's approaching sound, generating a modulation tone that leverages the 'missing fundamental' phenomenon to enhance recognition, while minimizing noise transmission by adjusting sound pressure and frequency components based on distance and surroundings, and incorporating a high-pass-filter function to further attenuate low-frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If high-frequency dummy sounds are produced by cutting low-frequency components, then the sounds can be transmitted far away without easy attenuation, but the pedestrians cannot properly recognize the dummy sounds such as tire noise or engine idling sound
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the frequency characteristics of dummy sounds based on vehicle speed. At low speeds, low-frequency components are emphasized to improve recognizability, while at high speeds, high-frequency components are enhanced for better transmission distance. This dynamic parameter adjustment resolves the contradiction between transmission distance and sound recognizability.
Solution Approach 2:
The system dynamically switches between different frequency emphasis strategies based on operating conditions (vehicle speed). The sound generation device transitions from emphasizing low-frequency components at low speeds to emphasizing high-frequency components at high speeds, making the system adaptive to different scenarios and resolving the static contradiction between transmission distance and recognizability.
2Loss of information
If low-frequency components are included in dummy sounds, then pedestrians can properly recognize the vehicle approach sound, but the sounds are easily attenuated and cannot be transmitted far away
Solution Approach 1:
The patent changes the frequency parameter distribution of dummy sounds based on vehicle speed. At low speeds where transmission distance is less critical, low-frequency components are included to enhance recognizability. At high speeds where transmission distance becomes critical, the system reduces low-frequency content and emphasizes high-frequency components, thus resolving the contradiction through context-dependent parameter adjustment.
3Reliability
If dummy sounds are produced to notify pedestrians of vehicle approach, then pedestrian safety is improved, but the superior silence advantage of low-noise vehicles is deteriorated
Solution Approach 1:
The patent applies local quality by directing sound energy preferentially toward pedestrian areas rather than omnidirectional noise distribution. The sound producing device is positioned and configured to emit dummy sounds primarily in the forward direction where pedestrians are most likely to be, thus improving safety notification while minimizing noise propagation to other areas and preserving the vehicle's silence advantage.
Solution Approach 2:
The system adjusts sound pressure level parameters dynamically based on vehicle speed and operating conditions. At very low speeds where the vehicle is naturally quiet, dummy sounds are generated only when necessary to maintain safety without excessive noise. At higher speeds where natural vehicle noise is already present, the dummy sounds blend with the existing noise profile, thus improving safety while minimizing the additional noise burden.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively produces recognizable approaching sounds for pedestrians, similar to the original tone, without excessive noise, by applying greater gains to higher frequency components and reducing low-frequency sound pressure, ensuring clear vehicle approach notification while minimizing noise transmission.
Implementation Method 1
generating a modulation tone that leverages the 'missing fundamental' phenomenon to enhance recognition
Implementation Method 2
a modulation-tone generating device generating a modulation tone from the original tone generated by the original-tone generating device with a comb filter function which is configured to apply gains to frequency components so that a gain to be applied to a specified frequency component of a times-tone row which has frequencies of n-times (n: an integer which is 2 or greater) of a fundamental frequency constituting the original tone is greater than that to be applied to the other frequency component than the specified frequency component of the times-tone row
Implementation Method 3
incorporating a high-pass-filter function to further attenuate low-frequency components
Data Source
AI summary
A sound producing apparatus for a vehicle notifying a vehicle's approach outside the vehicle comprising an original-tone generating portion generating an original tone of a vehicle's approaching sound for recognition of a vehicle's approach, a modulation-tone generating portion generating a modulation tone from the original tone with a comb filter function which is configured to apply gains to frequency components so that a gain to be applied to a specified frequency component of a times-tone row which has frequencies of n-times of a fundamental frequency is greater than that to be applied to the other frequency component than the specified frequency component of the times-tone row, a sound-pressure setting portion setting a sound pressure of the approaching sound of the modulation tone, and a speaker producing outside the vehicle the vehicle's approaching sound of the modulation tone with the set sound pressure.