In-Car Audio Equalization for Natural Sound and Howling Prevention
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Solution Overview
Problem
Existing in-car communication systems face challenges in maintaining natural sound quality while preventing howling, as the acoustic feedback characteristic from the speaker to the microphone is not flat, requiring gain reduction at specific frequencies, which degrades sound quality.
Innovation Solution
A frequency characteristics converting apparatus that estimates noise levels and adjusts the frequency characteristics of sound signals based on noise levels, prioritizing sound volume over sound quality in noisy conditions to prevent howling and maintain natural sound reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gain reduction is applied at specific frequencies to prevent howling, then howling is prevented, but sound quality is degraded
Solution Approach 1:
The patent applies dynamics by making the equalizer frequency characteristics adjustable rather than fixed. The system dynamically switches between a first equalizer setting (prioritizing howling prevention with gain reduction at feedback frequencies) and a second equalizer setting (prioritizing natural sound reproduction with flatter frequency response). This allows the system to adapt to different noise levels and acoustic conditions, resolving the contradiction between reliable howling prevention and high sound quality.
Solution Approach 2:
The patent changes the frequency characteristic parameters of the equalizer based on noise level detection. When noise exceeds a threshold, the system switches to frequency characteristics optimized for howling prevention; when noise is low, it switches to characteristics optimized for natural sound reproduction. This parameter change approach allows the same system to achieve both howling prevention and high sound quality under different operating conditions.
2Reliability
If equalization is performed with priority on howling prevention, then howling is prevented, but natural sound reproduction is degraded
Solution Approach 1:
The system dynamically adjusts the equalizer settings based on real-time noise level detection. In low-noise environments, the equalizer uses frequency characteristics that prioritize natural sound reproduction with minimal gain reduction. In high-noise environments, it switches to characteristics that prioritize howling prevention. This dynamic adaptation resolves the contradiction by allowing both modes to operate at different times based on conditions.
Solution Approach 2:
The patent implements parameter changes by switching between different equalizer frequency characteristic sets. The first set has gain reduction at frequencies prone to feedback for howling prevention, while the second set has flatter frequency response for natural sound. The noise detection unit triggers parameter changes between these sets, allowing the system to achieve both howling prevention and natural sound reproduction depending on the acoustic environment.
3Reliability
If fixed frequency characteristic equalization is used, then howling prevention is achieved, but adaptability to different noise levels is reduced
Solution Approach 1:
The patent transforms the fixed equalizer into a dynamic system that automatically adapts to different noise levels. The noise detection unit continuously monitors the acoustic environment and triggers switches between different equalizer frequency characteristic settings. This allows the system to maintain howling prevention capability across varying noise conditions while adapting to optimize sound quality for each specific environment.
Solution Approach 2:
The system uses parameter changes by switching between multiple pre-configured equalizer frequency characteristic sets. Each set is optimized for different noise conditions - one set for howling prevention in noisy environments, another for natural sound reproduction in quiet environments. The noise detection unit determines when to switch parameters, providing adaptability to different noise levels while maintaining reliable howling prevention when needed.
Data Source
AI summary
Provided are a frequency characteristics converting apparatus, a frequency characteristics converting method, and a program that make natural reproduced sound of a speaker compatible with howling prevention. In the frequency characteristics converting apparatus, a sound emitter is located at a first position on an inside of a vehicle, and in response to an increase in magnitude of noise at the first position, volume of target sound, collected by a sound collector installed at a second position, is increased when the target sound is emitted by the sound emitter, and a degree of signal processing that is applied to the target sound is increased.