Filter Generation for Sound Localization
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Solution Overview
Problem
Generating appropriate filters for sound localization is challenging due to variations in acoustic device delay and asymmetric measurement environments, leading to difficulties in synchronizing left and right transfer characteristics, especially when using general-purpose equipment like personal computers.
Innovation Solution
A filter generation device and method that includes left and right speakers, microphones, and a filter generation unit with a search unit to find direct sound arrival times, a determination unit to match amplitude signs, a correction unit to adjust cutout timing, and a cutout unit to generate filters, ensuring appropriate timing and balance between left and right sound fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If general-purpose equipment like PC is used for impulse response measurement, then ease of operation is improved, but measurement precision deteriorates due to variable acoustic device delay
Solution Approach 1:
The patent applies preliminary action by searching for and identifying the direct sound arrival time before performing the cutout operation. The search unit scans the transfer characteristics to locate the maximum amplitude point, which serves as the reference timing for subsequent filtering operations. This preliminary identification ensures that even with variable delays from general-purpose equipment, the correct synchronization point is found, thereby maintaining measurement precision while allowing ease of operation.
2Manufacturing precision
If cutout is performed at the same filter length and timing for left and right transfer characteristics, then manufacturing precision is improved, but adaptability deteriorates due to asymmetric measurement environments
Solution Approach 1:
The patent applies asymmetry by allowing different cutout timings for left and right transfer characteristics. Instead of forcing symmetric cutout at the same timing, the system independently determines the direct sound arrival time for each channel based on the maximum amplitude point in各自的 transfer characteristics. This asymmetric approach adapts to the specific measurement environment of each channel, maintaining precision while accommodating environmental variations.
Solution Approach 2:
The patent applies dynamics by making the cutout timing flexible rather than fixed. The search unit dynamically identifies the direct sound arrival time for each transfer characteristic, allowing the cutout point to adapt to the actual acoustic conditions. This dynamic timing adjustment enables the system to handle asymmetric measurement environments while maintaining consistent filter generation quality.
3Measurement precision
If direct sound arrival time is determined by maximum amplitude timing, then measurement precision is improved, but device complexity increases due to search and correction units
Solution Approach 1:
The patent applies self-service by using the transfer characteristics themselves to determine the direct sound arrival time. The search unit utilizes the maximum amplitude point within the transfer characteristics data to identify the timing, rather than requiring external reference signals or complex synchronization mechanisms. This self-referential approach improves precision while minimizing additional device complexity, as the system uses its own measurement data to guide the filtering process.
Data Source
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AI summary
A filter generation device according to an embodiment includes left and right speakers (5L, 5R), left and right microphones (2L, 2R), and a processor (210) that generates filters in accordance with transfer characteristics (Hls, Hlo, Hro and Hrs) from the left and right speakers (5L, 5R) to the left and right microphones (2L, 2R) based on sound pickup signals. The processor (210) includes a direct sound arrival time search unit (214) that searches for a direct sound arrival time by using a time at which an absolute value of an amplitude reaches its maximum, a left and right direct sound determination unit (215) that determines whether signs of amplitudes at the direct sound arrival time match, an error correction unit (216) that, when the signs do not match, corrects cutout timing so that the direct sound arrival times coincide, and a waveform cutout unit (217) that cuts out the transfer characteristics.