Adaptive Filterbanks for Psychoacoustic Frequency Range Extension
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The bandwidth of loudspeakers and headphones is often limited to a sub-domain of the human auditory system's bandwidth, particularly in the low frequency region, making it difficult to produce the impression of frequencies beyond their physical capabilities.
Innovation Solution
A system using adaptive nonlinear filterbanks generates phase-coherent harmonic spectra by applying a nonlinearity with scale-dependent constraints, allowing speakers to produce a psychoacoustic impression of frequencies outside their physical range without hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the speaker's physical bandwidth is used as-is, then the speaker operates within its designed capabilities, but it cannot produce frequencies beyond its physical range
Solution Approach 1:
The patent introduces an intermediary processing system (filterbank, nonlinearity application, spectral transformation) that mediates between the input audio signal and the speaker output. This intermediary creates virtual frequency components through signal processing, allowing the speaker to produce frequencies beyond its physical capabilities while maintaining perceptual accuracy through psychoacoustic principles
Solution Approach 2:
The patent replaces the mechanical limitation of the speaker's physical bandwidth with a signal processing approach. Instead of relying on the speaker's mechanical ability to reproduce all frequencies, the system uses digital signal processing (filterbanks, spectral transformations, nonlinearity) to generate frequencies that the speaker cannot physically produce, substituting mechanical capability with computational methods
2Adaptability or versatility
If high-quality speakers with extended bandwidth are used, then frequency coverage is improved, but device cost and complexity increase
Solution Approach 1:
The patent creates virtual copies of frequency components through signal processing. Instead of using physical speakers capable of reproducing all frequencies, the system generates spectral copies and transformations of the input signal that simulate the presence of frequencies beyond the speaker's physical range, using computational methods to create perceptual equivalents
Solution Approach 2:
The patent transforms the audio signal through parameter changes in the frequency domain. By applying spectral transformations, rotating the spectrum, and modifying frequency components through nonlinear operations, the system changes the signal parameters to create virtual frequency content that appears natural to human listeners despite being generated through processing rather than direct speaker reproduction
3Adaptability or versatility
If the speaker operates at maximum power to extend effective range, then frequency coverage improves, but power consumption increases and speaker longevity decreases
Solution Approach 1:
The patent performs preliminary signal processing to generate the required frequency components before they reach the speaker. By pre-processing the audio signal through filterbanks and spectral transformations to create virtual frequency content, the system eliminates the need for the speaker to operate at maximum power to achieve full frequency coverage, reducing energy consumption and thermal stress on the speaker
Data Source
AI summary
A system provides for psychoacoustic frequency range extension. The system generates quadrature components from an audio channel, and generates rotated spectral quadrature components by applying a forward transformation that rotates a spectrum of the quadrature components from a standard basis to a rotated basis. In the rotated basis, the system isolates components of the rotated spectral quadrature components at target frequencies, and generates weighted phase-coherent harmonic spectral quadrature components by applying a nonlinearity to the isolated components having a dependence on scale that is subject to constraints. The circuitry generates a harmonic spectral component by applying an inverse transformation that rotates a spectrum of the weighted phase-coherent harmonic spectral quadrature components from the rotated basis to the standard basis. The circuitry combines the harmonic spectral component with frequencies of the audio channel outside of the target frequencies to generate an output channel, and provides the output channel to a speaker.