Digital Audio Processing for Adaptive Low-Frequency Excursion Control
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Solution Overview
Problem
Existing methods for enhancing low-frequency audio reproduction risk damage to transducers due to excessive excursion, particularly in small loudspeakers or seat-integrated transducers, by amplifying low frequencies beyond their maximum excursion limits.
Innovation Solution
A method involving high-pass filtering and adaptive low shelf filtering to dynamically adjust amplification gains based on estimated excursion values, ensuring the transducer does not exceed its maximum excursion while enhancing low-frequency sound rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amplification filtering is applied to reinforce low frequencies, then sound reproduction quality is improved, but transducer excursion increases causing risk of damage
Solution Approach 1:
The patent applies dynamic excursion management by continuously monitoring the transducer's excursion value and adjusting the amplification gain in real-time. When the estimated excursion exceeds a predefined threshold, the system reduces or cancels the amplification gain, preventing diaphragm damage while maintaining optimal sound reproduction quality under normal conditions.
Solution Approach 2:
The system implements feedback control by estimating the transducer's excursion value based on the amplified signal characteristics and using this information to adjust the amplification gain dynamically. This closed-loop approach ensures that low-frequency enhancement is applied only when safe, preventing transducer damage while improving sound quality.
2Manufacturing precision
If amplification gain is increased for low frequencies, then rendering of low frequencies is improved, but excursion of the transducer exceeds maximum value
Solution Approach 1:
The patent dynamically adjusts the amplification gain based on real-time estimation of transducer excursion. The system switches between different gain states (first gain for safe operation, second gain for enhanced reproduction) depending on whether the estimated excursion remains within safe limits, thereby optimizing low-frequency rendering without exceeding maximum excursion.
Solution Approach 2:
The system changes the amplification gain parameter dynamically based on excursion conditions. When excursion is within safe limits, a higher amplification gain is applied to enhance low-frequency reproduction. When excursion approaches dangerous levels, the gain is reduced or canceled, preventing excessive diaphragm movement while maintaining audio quality.
3Manufacturing precision
If very low frequencies are amplified, then full spectrum coverage is achieved, but audible benefit is minimal while excursion risk increases
Solution Approach 1:
The patent applies amplification selectively to specific frequency ranges that provide audible benefit. By analyzing the spectral content and applying targeted amplification to frequencies that are both audible and contribute meaningfully to sound quality, the system avoids amplifying extremely low frequencies that offer minimal audible benefit but significantly increase excursion risk.
Solution Approach 2:
The system applies partial amplification only to the necessary frequency ranges rather than uniformly amplifying all low frequencies. This selective approach enhances audible frequencies while limiting the amplification of sub-audible very low frequencies that contribute to excursion without providing proportional audible benefit.
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
Protects transducers from damage while improving the reproduction of low and medium frequencies without introducing non-linear distortion.
Implementation Method 1
performing a high-pass filtering of the digital audio signal having an associated filtering frequency, the filtering frequency being greater than or equal to 10 Hz and less than two thirds of the specific cutoff frequency of the transducer
Implementation Method 2
applying, to said filtered digital audio signal, a first low shelf filter, said first low shelf filter performing an amplification of the frequencies, comprised in a frequency range that is less than a predetermined limit frequency
Implementation Method 3
a magnetic element capable of generating vibrations based on the frequency of the audio signal provided as input. For example, for a loudspeaker, the magnetic element consists of a coil, in which an electric current is passed, submerged in a magnetic field created by pole pieces and a magnet
Data Source
AI summary
A method implemented in an audio system including a transducer having a magnetic element suitable for generating vibrations based on the frequency of the audio signal. The method is implemented by one or more processing chains including: A) a high-pass filtering of the digital audio signal having a frequency greater than or equal to 10 Hz and less than two thirds of the specific cutoff frequency of the transducer; B) performing a first low shelf filtering with a predetermined first amplification gain; C) estimating an excursion value of the transducer for the signal obtained after applying the first low shelf filter; D) if the estimated excursion value of the transducer exceeds the maximum excursion value, calculating a second amplification gain that is less than the first gain; and E) applying a second low shelf filtering of gain equal to the second calculated gain.