Vehicle Engine Sound Reproduction with Harmonic Phase Smoothing
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Solution Overview
Problem
Existing engine harmonic enhancement methods that rely solely on magnitude are insufficient to generate a natural-sounding engine sound, as they fail to account for the initial phase differences between harmonics, leading to inadequate reproduction of specific engine sound characteristics.
Innovation Solution
The method involves performing harmonic decomposition to extract phase and shape information for each harmonic over a range of RPM, introducing a distortion signal with the same standard deviation as the original sound to preserve natural variations, and using these parameters to generate an engine harmonic enhancement signal that can be added to a baseline engine sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If harmonic generation based on magnitude only is used, then the enhancement level can be increased, but the naturalness of the engine sound deteriorates
Solution Approach 1:
The patent changes the parameters used in harmonic generation from magnitude-only to include both magnitude and phase information. By extracting and utilizing phase information from the target engine sound across multiple RPM points, the system achieves high enhancement levels while maintaining naturalness. The phase information is integrated into the harmonic generation process to accurately reproduce the temporal characteristics of the original engine sound.
2Manufacturing precision
If initial phase difference between harmonics is introduced, then some naturalness can be improved, but the ability to reproduce specific engine sound character deteriorates
Solution Approach 1:
The patent performs preliminary extraction of phase information from the target engine sound at multiple RPM points before the enhancement process. This pre-extracted phase information is stored and then applied during harmonic generation to ensure both naturalness and accurate reproduction of specific engine sound characteristics. The phase information is prepared in advance to guide the harmonic synthesis process.
Solution Approach 2:
The system dynamically adapts the phase information to different RPM conditions. By extracting phase information at multiple RPM points (e.g., 1000, 2000, 3000, 4000, 5000, 6000 RPM) and selecting or interpolating the appropriate phase data based on current engine operating conditions, the system maintains both naturalness and specificity across varying engine speeds.
3Measurement precision
If phase information is extracted for each harmonic, then the reproduction accuracy improves, but the system complexity increases
Solution Approach 1:
The patent segments the engine sound analysis into discrete harmonics, extracting magnitude and phase information for each harmonic component individually. This segmentation allows for precise control over each harmonic's contribution to the overall sound while managing complexity through systematic processing of individual components rather than treating the sound as a whole.
Solution Approach 2:
The system creates a digital model (copy) of the target engine sound's phase characteristics across multiple RPM points. This copied phase information is then applied during enhancement without requiring physical modification of the engine or sound sources, reducing system complexity while maintaining high reproduction accuracy.
Data Source
AI summary
An RPM signal representing a current RPM of a vehicle engine is received. An instant magnitude and an instant phase are determined for each of N harmonics of a target engine sound based on the RPM signal. The instant magnitude and the instant phase are each smoothed to generate a smoothed harmonic magnitude and a smoothed harmonic phase for each of the N harmonics. A magnitude perturbation signal and a phase perturbation signal are generated for each of the N harmonics. An individual harmonic signal is also generated for each of the N harmonics based, at least in part, on the smoothed harmonic magnitude, the magnitude perturbation signal, the smoothed harmonic phase, and the phase perturbation signal. The individual harmonic signals are summed to generate an engine harmonic enhancement signal, and the engine harmonic enhancement signal is transduced to acoustic energy.