Virtual Bass Signal Processing for Small Speaker Audio Quality
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Solution Overview
Problem
Conventional methods for enhancing bass performance in small loudspeakers, such as amplification and virtual pitch techniques, face issues like intermodulation distortion and incorrect pitch perception, leading to degraded audio quality.
Innovation Solution
An apparatus that transforms an audio signal into frequency components, extracts the bass portion, estimates the fundamental frequency, and shifts it by an integer multiple to create a virtual bass signal, which is then added back to the original signal, ensuring efficient production and maintaining harmonic structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If low-frequency components are amplified to improve bass performance, then bass loudness is improved, but speaker efficiency deteriorates and energy consumption increases
Solution Approach 1:
The patent creates virtual bass by synthesizing harmonic copies of the fundamental low-frequency tone. Instead of directly reproducing the fundamental frequency F0, the system generates harmonics at frequencies 2F0, 3F0, 4F0, etc., which the human ear perceives as the original pitch. This allows small speakers to produce bass perception without physically moving air at low frequencies, dramatically improving energy efficiency.
Solution Approach 2:
The patent transforms the audio signal from time domain to frequency domain using Fourier transform, identifies and manipulates specific frequency components (harmonics), then reconstructs the signal. By changing the frequency domain parameters and selectively enhancing harmonic components while maintaining the fundamental pitch perception, the system achieves bass enhancement without the energy costs of direct low-frequency amplification.
2Illumination intensity
If low-frequency amplification is applied to enhance bass, then bass perception is improved, but speaker reliability deteriorates due to excessive coil excursion
Solution Approach 1:
The system synthesizes harmonic copies (2F0, 3F0, 4F0, etc.) of the fundamental bass tone and uses these to create the perception of low-frequency sound. Since small speakers cannot efficiently produce low frequencies anyway, using harmonic copies at higher frequencies avoids the mechanical stress and coil excursion problems that would occur with direct low-frequency amplification, thereby protecting speaker reliability.
3Illumination intensity
If nonlinear devices are used to generate harmonics for virtual bass, then bass enhancement is achieved, but audio quality deteriorates due to intermodulation distortion
Solution Approach 1:
The patent replaces nonlinear mechanical processing with linear digital signal processing. Instead of using nonlinear devices that physically generate harmonics through distortion, the system uses Fourier transform to analytically identify and extract harmonic components, then selectively enhances them through linear filtering and synthesis. This substitution of digital analysis for physical nonlinear processing eliminates intermodulation distortion while maintaining bass enhancement.
Solution Approach 2:
The patent introduces the Fourier transform as an intermediary tool to analyze the audio signal in the frequency domain. This intermediary allows precise identification of harmonic components without the need for nonlinear processing. By using this mathematical intermediary, the system can selectively enhance desired harmonics while filtering out unwanted distortion products, thereby maintaining high audio quality.
4Illumination intensity
If phase vocoder frequency scaling is applied to create virtual bass, then bass perception is generated, but pitch accuracy deteriorates
Solution Approach 1:
The patent applies frequency scaling selectively only to the harmonic components above the fundamental frequency, while preserving the fundamental frequency relationship. By scaling harmonics to frequencies 2F0, 3F0, 4F0 (exact integer multiples) rather than applying uniform scaling, the system maintains accurate pitch perception. The selective action on specific frequency components preserves pitch accuracy while still creating virtual bass perception.
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 approach provides a more realistic and improved bass impression without the limitations of traditional methods, enhancing audio output quality, especially in speakers with poor bass production capabilities.
Implementation Method 1
For a simple example to illustrate this effect, consider a pitch with a fundamental frequency F0 of 100 Hertz (Hz). While the sensation of a 100 Hz pitch can by produced in the human ear by playing a pure tone of 100 Hz, musical instruments and human vocal cords usually produce this sensation using a set of tones with a complex harmonic structure, such as 100 Hz, 200 Hz, 300 Hz, etc., which can also provide a fuller (and differentiated) sound quality. What is more interesting is that the tone at the fundamental frequency of 100 Hz is not necessary for people to have the sensation of hearing a 100 Hz pitch. Even if the tone of 100 Hz is missing, a set of harmonic tones at 200 Hz, 300 Hz, 400 Hz, etc., can still produce the sensation of a 100 Hz pitch. The human ear apparently can infer the pitch from the harmonic tones alone. This phenomenon is referred to as virtual pitch.
Data Source
AI summary
Provided are, among other things, systems, methods and techniques for processing an audio signal to add virtual bass. In one representative embodiment, an apparatus includes: (a) an input line that inputs an original audio signal; (b) a bass extraction filter that extracts a bass portion of such original audio signal; (c) an estimator that estimates a fundamental frequency of a bass sound within such bass portion; (d) a frequency translator that shifts the bass portion by a positive frequency increment that is an integer multiple of the fundamental frequency estimated by the estimator, thereby providing a virtual bass signal; (f) an adder having (i) inputs coupled to the original audio signal and to the virtual bass signal and (ii) an output; and (g) an audio output device coupled to the output of the adder.