Virtual Engine Sound Phase Compensation for Embedded Systems
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Solution Overview
Problem
Phase vocoders used in electronic active sound design for electric vehicles face challenges in maintaining vertical phase coherence, leading to loss of transient phenomena and requiring high computational resources and memory, making them difficult to implement in embedded systems with limited calculation and memory capacity.
Innovation Solution
A virtual engine sound generating device that uses a time delay value to compensate for phase changes in sound sources, employing a signal generating unit that processes sound source information through analysis and synthesis frames with fixed delay values, windowing, FFT, phase compensation, and IFFT to maintain phase coherence across all frequencies, and a low pass filter to eliminate phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phase vocoder is used to change sound source length, then natural length change is achieved, but vertical phase coherence is lost and transient phenomena disappear
Solution Approach 1:
The patent changes the fundamental parameter from predictive phase correction to fixed time delay-based phase compensation. By using a fixed delay value corresponding to the frame interval and applying linear phase compensation across all frequency components, the patent maintains vertical phase coherence while achieving sound source length change, resolving the contradiction between natural length change and phase coherence preservation
2Measurement precision
If phase vocoder with narrow frame gap is used for high-quality sound expansion, then accurate frequency prediction is achieved, but large amount of calculation is required
Solution Approach 1:
The patent extracts and removes the complex predictive frequency estimation and phase correction process from the phase vocoder. By using a fixed delay value and applying simple linear phase compensation to all frequency components simultaneously, the patent eliminates the need for iterative prediction and correction, dramatically reducing calculation amount while maintaining processing accuracy
Solution Approach 2:
The patent segments the processing into fixed intervals using a predetermined frame interval and fixed delay value. This segmentation allows parallel processing of all frequency components at each frame, avoiding the sequential predictive correction required by traditional phase vocoders and reducing overall computational burden
3Adaptability or versatility
If phase vocoder is implemented in embedded controller, then EASD function is achieved, but memory usage is large due to two-frame frequency response storage
Solution Approach 1:
The patent extracts and eliminates the requirement to store frequency responses of two frames. By using a fixed delay value and applying phase compensation based on a single frame's frequency components, the patent reduces memory requirements from storing multiple frame data to storing only the current frame and fixed delay parameters
Solution Approach 2:
The patent performs preliminary action by pre-determining the frame interval and calculating the fixed delay value in advance. This allows the system to operate with minimal real-time memory storage, as the delay value is prepared beforehand and does not require dynamic storage of multiple frame responses during processing
4Measurement precision
If phase vocoder with maximum frequency detection and prediction control is used, then accurate frequency correction is achieved, but implementation with hardware accelerator is difficult
Solution Approach 1:
The patent changes the control parameter from dynamic maximum frequency detection and prediction to a fixed delay value-based approach. By using a predetermined delay corresponding to the frame interval and applying uniform linear phase compensation across all frequencies, the patent simplifies the control process to be easily implementable in hardware accelerators while maintaining correction accuracy
Solution Approach 2:
Instead of detecting maximum frequency and predicting accurate frequency through complex control processes, the patent inverts the approach by applying fixed delay-based phase compensation to all frequency components simultaneously. This inversion simplifies the control logic and makes hardware accelerator implementation straightforward while achieving accurate phase correction
Data Source
AI summary
Provided are a virtual engine sound generating device for an embedded system and a control method thereof. The virtual engine sound generating device includes an input unit receiving sound source information, a signal generating unit compensating for a phase for each frequency with respect to all frequencies of the sound source information to generate corrected sound source information, and an output unit providing final sound source information based on the corrected sound source information.