Dual-Microphone Acoustic Reproduction for Stable Transfer Functions

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Solution Overview

Problem

Existing noise-cancelling systems using multiple microphones for active noise reduction face challenges in maintaining stable transfer functions and are prone to howling, especially when collecting sound from different acoustic spaces.

Innovation Solution

The use of multiple microphones positioned strategically within the acoustic reproduction apparatus, with one microphone closer to the driver unit and another closer to the eardrum, along with specific filter configurations for high and low-frequency components, to generate noise-cancelling signals that stabilize transfer functions and prevent howling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple microphones are used to collect sound from different acoustic spaces, then noise cancellation performance is improved, but transfer function stability deteriorates and howling occurs

Engineering Contradiction:

Improvenoise cancellation performanceVSAvoidtransfer function stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent divides the noise cancellation system into separate frequency bands by assigning different microphones to different frequency ranges. The first microphone handles high-frequency components while the second microphone handles low-frequency components, allowing each microphone to operate in an optimized acoustic space without causing transfer function instability or howling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different microphones are positioned at different locations within the acoustic reproduction apparatus to collect sound from different acoustic spaces. The first microphone is positioned to collect high-frequency noise while the second microphone is positioned to collect low-frequency noise, with each position optimized for its specific frequency range to maintain transfer function stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If microphones are positioned closer to the eardrum, then noise cancellation at the eardrum position is improved, but transfer function changes become more likely

Engineering Contradiction:

Improvenoise reduction at eardrum positionVSAvoidtransfer function stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent segments the noise collection task by frequency bands and spatial positions. Low-frequency noise is collected by a microphone positioned closer to the eardrum where it has better noise cancellation effect, while high-frequency noise is collected by a microphone positioned closer to the driver unit where the transfer function is more stable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the operational parameters of different microphones by assigning different frequency response characteristics. The first microphone is configured to process high-frequency components while the second microphone processes low-frequency components, allowing each microphone to operate in an acoustic space where its transfer function remains stable.

Inventive Principle:

Principle #35Parameter changes

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

This configuration enhances noise cancellation performance by stabilizing transfer functions and preventing howling, resulting in improved noise reduction at the eardrum position.

Implementation Method 1

external noise (noise) is collected by a microphone as acoustic-electric conversion means

Methodology Applied

Scientific EffectAcoustic-electric conversion:

Implementation Method 2

a noise-cancelling signal acoustically opposite in phase to the noise is generated from an acoustic signal of the collected noise

Methodology Applied

Scientific EffectActive noise reduction:

Implementation Method 3

a driver unit configured to perform acoustic output on the basis of the noise-cancelling signal

Methodology Applied

Scientific EffectAcoustic output:

Data Source

PatentUS20250308503A1Acoustic reproduction apparatus, signal processing apparatus, and signal processing method

Publication Date: 2025.10.02 SONY GROUP CORP

AI summary

Provided is an acoustic reproduction apparatus, including a first microphone to be used for noise cancellation processing using a feedback scheme, a second microphone including a sound collection surface in a direction different from a direction of a sound collection surface of the first microphone and to be used for noise cancellation processing using the feedback scheme, and an acoustic signal processing unit configured to generate a noise-cancelling signal using a first sound collection signal collected by the first microphone and a second sound collection signal collected by the second microphone.