Feed-Forward Tone Control for Fast Level Changes Without Clipping
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Solution Overview
Problem
Conventional sound quality adjustment devices experience delayed level boost adjustments, leading to potential clipping issues when input sound signals rapidly increase, due to feedback control mechanisms.
Innovation Solution
A sound quality adjustment device employing a feed-forward arrangement with a filter circuit, boost circuit, and adder for dynamic range expansion/contraction, along with a decay processing circuit to manage rapid level variations and prevent clipping, while ensuring smooth frequency connections and natural auditory sensations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is used to adjust level boost amounts based on detected sound signal levels, then sound quality adjustment can be achieved, but the adjustment is delayed relative to rapid level variations causing clipping
Solution Approach 1:
The patent applies preliminary action by detecting the level of the input sound signal before it passes through the tone filters and boost circuits. The level detection section measures the input signal level in advance, and this detected level is immediately used to control the boost amount of the tone filters. This pre-detection approach eliminates the delay inherent in feedback control systems that wait for the signal to pass through the entire processing chain before making adjustments.
Solution Approach 2:
The patent implements a control mechanism where the detected input signal level feeds forward to adjust the boost amount of the tone filters. While not traditional feedback (which would measure output and adjust input), the system uses real-time level detection to dynamically control the boost circuits, creating a responsive control loop that adjusts parameters based on current signal conditions without the delays of conventional feedback systems.
2Ease of operation
If the level boost amount is rapidly increased to enhance sound quality, then desired sound quality adjustment is achieved, but clipping may result due to overflow of digital signal processing
Solution Approach 1:
The patent applies preliminary anti-action by detecting the input signal level before processing and using this information to pre-adjust the boost amount of the tone filters. The level detection section measures the input signal characteristics in advance, and the boost amount calculation section determines appropriate boost levels based on these measurements. This prevents excessive boosting that would cause clipping by controlling the boost amount according to the actual input signal level before the signal passes through the enhancement circuits.
Data Source
AI summary
LPF and HPF extract bass and treble ranges, respectively, from an input sound signal, and bass and treble boost circuits perform dynamic range expansion/contraction on the extracted bass- and treble-range sound signals in accordance with input levels of the sound signals. The input sound signal and the sound signals output from the boost circuits are added together. There may also be provided coefficient calculation sections for calculating filter coefficients on the basis of the levels of the sound signals extracted by the LPF and HPF. In this case, the bass and treble boost sections perform, in accordance with the filter coefficients calculated by the corresponding coefficient calculation sections, filter processes for increasing/decreasing the levels of the bass and treble ranges, respectively.