FIR Filter Phase Conversion for Pre-Echo Reduction
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Solution Overview
Problem
Conventional IIR filters have low frequency resolution, making it difficult to accurately compensate for sound signal frequency characteristics, and while FIR filters offer high frequency resolution, they generate pre-echoes when used for this purpose.
Innovation Solution
A signal processing device that measures impulse responses between speakers and a listening position, applies Fourier transforms to obtain frequency spectra, calculates phase adjustment amounts, detects leading phase bands, converts their phase to lagging, and generates filter coefficients to reduce pre-echoes and improve sound quality using an FIR filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an IIR filter is used to compensate for frequency characteristics, then the device complexity is reduced, but the frequency resolution is low making it difficult to accurately compensate
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and processes each band separately with its own FIR filter. This allows high frequency resolution through detailed spectral analysis while managing complexity by dividing the overall filtering task into independent band-specific operations rather than requiring a single complex full-band filter
Solution Approach 2:
The patent transitions from time-domain filtering (IIR) to frequency-domain processing by applying Fourier transforms. This dimensional change from time to frequency domain enables high frequency resolution through spectral analysis while using FIR filters that can be designed with specific frequency responses, resolving the contradiction between resolution and complexity
2Measurement precision
If an FIR filter is used to accurately compensate for frequency characteristics, then the frequency resolution is high, but pre-echoes are generated
Solution Approach 1:
The patent applies different phase adjustments to different frequency bands based on local characteristics. By detecting leading phase bands specifically and applying phase conversion only where needed rather than uniformly across all frequencies, the system maintains high frequency resolution where required while minimizing pre-echo generation through localized phase correction
Solution Approach 2:
The patent changes the phase parameter of the FIR filter coefficients through phase conversion of leading phase bands to lagging phases. This parameter modification allows the system to maintain the high frequency resolution capability of FIR filters while reducing pre-echo effects by adjusting the phase characteristics of specific frequency components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces pre-echoes and improves sound pressure and quality by compensating sound signal frequency characteristics while minimizing the negative effects of pre-echoes, enhancing the acoustic system's performance.
Implementation Method 1
a Fourier transformer configured to obtain a frequency spectrum corresponding to each of the plurality of speakers by applying a Fourier transform to the impulse responses corresponding to each of the plurality of speakers, respectively
Data Source
AI summary
A signal processing device according to aspects of the present disclosures comprises a measuring section configured to measure an impulse response between each of a plurality of speakers and a predetermined listening position, a Fourier transformer configured to obtain a frequency spectrum corresponding to each of the plurality of speakers by applying a Fourier transform, a phase adjustment amount calculator configured to calculate a phase adjustment amount for each frequency, a band detector configured to detect a leading phase band, a phase converter configured to convert a phase of the leading phase band to a lagging phase, and a filter coefficient generator configured to generate a filter coefficient based on the phase adjustment amount after conversion by the phase converter.