Virtual Engine Sound Control With Shepard Tone RPM Matching
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Solution Overview
Problem
Existing virtual engine sound generating systems using Shepard tones fail to accurately match engine power changes with actual driving conditions, leading to a mismatch between the virtual and real driving experiences, resulting in degraded driving emotion due to frequency changes and loss of high-frequency components during acceleration.
Innovation Solution
A virtual engine sound generating system that applies Shepard tones by superposing sine waves separated by octaves, adjusts frequencies based on RPM, and adds low-frequency tones to maintain a continuous sense of acceleration without reaching frequency upper limits, ensuring a continuous phase and preventing clicking noise, while adjusting amplitudes using accelerator pedal and vehicle speed information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Shepard tone is applied to generate virtual engine sound, then the auditory illusion of continuous acceleration is improved, but the frequency changes over time even at fixed RPM causing mismatch with actual driving conditions
Solution Approach 1:
The patent dynamically adjusts the Shepard tone frequency based on real-time RPM data from the engine control unit. Instead of using a fixed frequency Shepard tone that drifts over time, the system continuously synchronizes the tone frequency with the actual engine RPM, ensuring the virtual sound remains accurately matched to the actual driving conditions while maintaining the auditory illusion of continuous acceleration.
2Speed
If the Shepard tone frequency increases continuously, then the sense of acceleration is improved, but the high-frequency components are lost when reaching the upper frequency limit
Solution Approach 1:
The patent implements periodic octave transitions in the Shepard tone generation. When the frequency approaches the upper limit, the system transitions to the next octave range, resetting the frequency to a lower value while maintaining the perceptual illusion of continuous ascent. This periodic octave wrapping prevents high-frequency component loss while preserving the continuous acceleration sensation.
3Reliability
If multiple sine waves are superposed to create Shepard tone, then the auditory illusion effect is improved, but the complexity of the sound generation system increases
Solution Approach 1:
The patent segments the Shepard tone generation into distinct functional modules: a basic signal generating unit that creates individual sine waves at different octaves, an intermediate signal generating unit that combines these waves with appropriate amplitude modulation, and a final signal generating unit that integrates all components. This segmentation maintains the complex auditory illusion effect while organizing the system architecture for easier implementation and maintenance.
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 system provides a continuous acceleration feeling and improved driving immersion by maintaining frequency and bandwidth increases with RPM, preventing high-frequency component loss and matching the actual engine sound characteristics, thus enhancing the emotional quality of the driving experience.
Implementation Method 1
A Shepard tone is a sound that creates an illusion of sound (hearing hallucination) by making sound be heard to ascend or descend continually. A range that makes up the Shepard tone is called a Shepard range.
Implementation Method 2
This Shepard tone is a sound consisting of a superposition of a plurality of sine waves separated by octaves
Implementation Method 3
an intermediate signal generating unit receiving a plurality of output frequency signals having an octave intervals by applying a preset number of Shepard tones from the basic signal generating unit and combining the plurality of output frequency signals
Implementation Method 4
generating an engine sound having a continuous sense of acceleration in which the frequency increases by adding a low-frequency tone as the RPM increases
Implementation Method 5
a virtual engine sound generating unit generating a virtual engine sound by adding a plurality of output frequency signals corresponding to a plurality of predetermined order values applied to the engine
Data Source
AI summary
A virtual engine sound generating system and method involves generating a virtual engine sound with a Shepard tone by superposing sine waves separated by octaves, which causes an auditory illusion as if an infinite musical scale is played, and gives a driver a feeling that engine power continually increases.