Frequency-Selective Loudness Control for Balanced Audio Output
Solution Overview
Problem
Conventional acoustic signal processing systems fail to maintain balanced loudness perception across frequency bands when reducing volume, leading to uneven frequency response and potential speaker damage from excessive high-frequency components.
Innovation Solution
An acoustic signal processing apparatus that dynamically controls the high and low frequency components of an acoustic signal based on detected volume levels, using separate gain adjustments for each frequency band to maintain balanced loudness perception and prevent speaker damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the whole volume is reduced on an acoustic apparatus, then the loudness perception is improved, but the balance of the whole loudness perception deteriorates because tones based on low frequencies and high frequencies are hard to be heard
Solution Approach 1:
The patent applies local quality by differentiating the treatment of frequency bands. Instead of uniformly reducing all frequencies, the system applies frequency-dependent gain adjustment where low and high frequency components are emphasized relative to mid frequencies when volume is reduced, maintaining balanced loudness perception across different frequency ranges
Solution Approach 2:
The patent implements dynamics by making the gain adjustment adaptive to the set tone volume. The frequency-dependent gain is dynamically modified based on the volume level, automatically emphasizing low and high frequencies more when the overall volume is reduced, and reducing this emphasis when volume is increased, thus maintaining balanced perception across different operating conditions
2Stability of the object's composition
If the gain of low frequencies and high frequencies is increased to compensate human auditory sense, then the balance of loudness perception is improved, but the complexity of the control system increases
Solution Approach 1:
The patent applies universality by integrating the frequency-dependent gain adjustment functionality within the existing volume control mechanism. The same control system that manages overall volume also handles frequency balance compensation, eliminating the need for separate control circuits and reducing overall system complexity while maintaining balanced loudness perception
3Device complexity
If uniform gain is applied to high and low frequency components, then the device complexity is reduced, but the frequency response becomes inappropriate for different volume levels
Solution Approach 1:
The patent applies local quality by implementing frequency-dependent gain adjustment where different frequency bands (low, mid, high) receive different gain values. This ensures that each frequency band is appropriately controlled according to its characteristics and the set volume level, achieving accurate frequency response without requiring complex multi-band processing systems
Data Source
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AI summary
An acoustic signal's high frequency component extracted by an HPF 13 is multiplied in a multiplier 16 by the first coefficient to control the level of the high frequency component. The first coefficient is generated by a coefficient generation portion 21 in accordance with the full band level of an output signal. A low frequency component extracted by an LPF 15 is multiplied in a multiplier 17 by the second coefficient to control the level of the low frequency component. The second coefficient is generated by a coefficient generation portion 24 in accordance with the level of the output signal's low frequency component extracted by an LP filter 22. The level control of the low frequency component of the output signal and the level control of the high frequency component of the output signal are done separately, resulting in the loudness control which is suitable for the characteristic of the acoustic signal.