Vehicle Counting via Phase Curve Analysis
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Solution Overview
Problem
Conventional techniques fail to accurately determine the number of vehicles around a user vehicle due to the similarity in sound pressure levels across different frequency bands, especially when high-frequency bands include tire friction sounds, making it difficult to distinguish between one or multiple vehicles.
Innovation Solution
A vehicle counting device that analyzes surrounding sounds using a frequency analysis unit, selects vehicle sound candidates based on sound pressure thresholds, calculates phase curves indicating time dependency, and classifies these curves to determine the number of nearby vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sound pressure level signal in high frequency band (1000 Hz) is used to detect approaching vehicles, then vehicle approach detection is possible, but vehicle number determination becomes impossible due to tire friction sounds extending over wide frequency range (800-1200 Hz)
Solution Approach 1:
The patent segments the sound detection task into two distinct parts: (1) using sound pressure level in high frequency band for vehicle approach detection, and (2) using phase curve analysis for vehicle number determination. This segmentation allows each method to be optimized for its specific purpose without interference from the other.
Solution Approach 2:
The patent transitions from analyzing only sound pressure level (one dimension) to incorporating phase information (another dimension). By calculating phase curves and analyzing their temporal patterns, the system can distinguish between single and multiple vehicles even when their sound pressure signatures overlap in the frequency domain.
2Device complexity
If sound pressure information of specific frequency is used to distinguish vehicles, then processing is simple, but vehicle distinction becomes difficult due to small SN ratio and environmental noise
Solution Approach 1:
The patent introduces phase curve analysis as an intermediary method between simple sound pressure measurement and complex spectral analysis. The phase curve serves as a mediator that captures temporal patterns of vehicle sounds, providing sufficient discrimination power while maintaining relatively simple processing requirements.
Solution Approach 2:
The patent changes the analyzed parameter from sound pressure level to phase information. By focusing on phase characteristics and their temporal evolution rather than amplitude, the system achieves better vehicle distinction capability while avoiding the complexities of full spectral analysis.
Data Source
AI summary
A vehicle counting device including: a frequency analysis unit that analyzes a frequency of a surrounding sound detected by a vehicle sound detection microphone; a vehicle sound candidate selection unit that selects, as one or more vehicle sound candidates, one or more sounds included in the surrounding sound, based on the analysis by the frequency analysis unit, each of the one or more sounds being in a frequency band where a sound pressure is greater than or equal to a predetermined threshold value; a phase curve calculation unit that calculates, for each of the one or more vehicle sound candidates, a phase curve; and a vehicle count determination unit that classifies the one or more phase curves into at least one group, based on shapes of the one or more phase curves, and determines a total number of the at least one group as the number of the nearby vehicles.