Audio Filter Transition Band Narrowing With Acoustic Attenuators

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Solution Overview

Problem

Existing audio filters with wide transition bands fail to provide high-quality sound and are difficult and expensive to design with narrow transition bands.

Innovation Solution

Combining digital/analog/acoustic filters with sound attenuating metamaterials to create a narrower transition band without increasing overall frequency response, using metamaterials to attenuate sound in specific frequency regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If analog or digital filters are designed with narrow transition bands, then sound quality is improved, but design difficulty and cost increase

Engineering Contradiction:
Improvetransition band widthVSAvoidfilter design complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines conventional audio filters (analog, digital, or acoustic) with sound-absorbing metamaterials to create a composite system. The metamaterials, with their specific acoustic impedance properties, work together with the filters to achieve narrow transition bands without requiring complex high-order filter designs, thus resolving the contradiction between transition band width and design complexity

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

Sound-absorbing metamaterials are introduced as an intermediary element between the filter and the acoustic environment. These metamaterials mediate the transition by absorbing specific frequency ranges, enabling the filter to achieve a narrower transition band without increasing the filter's own complexity

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional filters are used, then design is simpler, but transition bands are wide and sound quality is poor

Engineering Contradiction:
Improvefilter design easeVSAvoidtransition band width
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

By creating a composite system that integrates conventional filters with sound-absorbing metamaterials, the patent maintains the simplicity of conventional filter designs while adding the metamaterial component to achieve narrow transition bands, thus improving sound quality without sacrificing design ease

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The sound-absorbing metamaterials utilized in the patent often exhibit porous structures that enable acoustic absorption at specific frequencies. This porous characteristic allows the materials to effectively narrow the transition bands when combined with conventional filters, improving sound quality while maintaining design simplicity

Inventive Principle:
Principle #31Porous materials

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

Achieves a narrower transition band with maintained or reduced overall frequency response, improving sound quality and reducing design complexity and cost.

Implementation Method 1

a first sound attenuator located relative to the first transducer to attenuate sound from the first transducer

Methodology Applied
Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentEP3272133B1Narrowing audio filter transition band
Publication Date: 2026.03.25 NOKIA TECHNOLOGIES OY
  • EP3272133B1 patent drawingFigure 1~2
  • EP3272133B1 patent drawingFigure 3~4
  • EP3272133B1 patent drawingFigure 5

AI summary

An apparatus including a first audio filter;a first transducer connected to the first audio filter; and a first sound attenuator located relative to the first transducer to attenuate sound from the first transducer. The first audio filter includes a first transition frequency band. The first sound attenuator is configured to attenuate sound generated by the first transducer from audio signals through the first audio filter in a target frequency band, where a majority of the target frequency band is in the first transition frequency band.