Multiband Compressor Self-Tuning for Loudspeaker Distortion Control

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Solution Overview

Problem

Existing audio systems face challenges in preventing non-linear distortion in loudspeakers, which affects sound quality and can violate assumptions in Acoustic Echo Canceller processes, leading to echo leakage, and require manual tuning of multiband compressors and limiters that is time-consuming and costly.

Innovation Solution

An automated system that generates test signals to measure loudspeaker response, determining crossover frequencies, amplitude thresholds, and other parameters to optimize multiband compressor and limiter settings, ensuring operation within a linear range and minimizing loudness reduction, thereby preventing distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If manual tuning of multiband compressors and limiters is performed to prevent distortion, then audio quality is improved, but time consumption and cost increase

Engineering Contradiction:
Improveaudio qualityVSAvoidtuning time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The system performs self-tuning by automatically measuring loudspeaker distortion characteristics and adjusting multiband compressor and limiter parameters without human intervention. The processor generates test signals, measures harmonic distortion, and autonomously optimizes compression settings to prevent distortion while maintaining audio quality.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces manual tuning operations with an automated electronic system. A processor generates test signals, measures loudspeaker response through microphones, calculates distortion metrics, and automatically adjusts compressor/limiter parameters, substituting the manual mechanical tuning process with an electronic measurement and control system.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If multiband compressors and limiters are tuned to prevent distortion, then harmonic distortion is reduced, but loudness reduction increases

Engineering Contradiction:
Improvedistortion preventionVSAvoidloudness reduction
Core Design Contradiction:
Manufacturing precisionVSLoss of energy

Solution Approach 1:

The system dynamically adjusts multiple parameters of the multiband compressor and limiter including compression ratios, threshold levels, attack and release times, and crossover frequencies. By optimizing these parameters based on measured loudspeaker characteristics, the system achieves distortion prevention while minimizing unnecessary loudness reduction.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent applies different compression and limiting parameters to different frequency bands rather than uniform settings across the entire audio spectrum. Each band is tuned according to the specific distortion characteristics of the loudspeaker at that frequency, allowing precise distortion control while preserving overall loudness.

Inventive Principle:
Principle #3Local quality

3Productivity

If automated tuning system is implemented, then productivity is improved, but device complexity increases

Engineering Contradiction:
Improvetuning efficiencyVSAvoidsystem complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The processor serves multiple functions: generating test signals across different frequencies, measuring loudspeaker response through microphones, calculating harmonic distortion metrics, determining optimal compression parameters, and controlling the multiband compressor and limiter. This multi-functionality reduces the need for separate dedicated devices for each task.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the tuning system components including signal generation, measurement microphones, distortion analysis, and parameter control into an integrated system. The processor consolidates multiple functions that could operate as separate devices, reducing overall system complexity while maintaining automated tuning capability.

Inventive Principle:
Principle #5Merging (Combining)

Data Source

PatentEP3439325B1Automatically tuning an audio compressor to prevent distortion
Publication Date: 2020.09.09 BLACKBERRY LTD
  • EP3439325B1 patent drawingFigure 1
  • EP3439325B1 patent drawingFigure 2
  • EP3439325B1 patent drawingFigure 3

AI summary

A system and method automates the tuning of one or more multiband compressors or multiband limiters to minimize loudspeaker distortion. The system and method render one or more test loudspeaker signals that vary in frequency and in amplitude out of a loudspeaker and records the responses of the loudspeaker at a microphone. The system and method measure a distortion of the loudspeaker, relative to a frequency and an amplitude, with respect to the one or more test loudspeaker signals and a microphone signal and calculate tunable parameters of the multiband compressor that includes cutoff frequencies in response to the measured distortion.