Virtual Bass Generation via Frequency Translation
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Solution Overview
Problem
Existing techniques for enhancing bass performance in small loudspeakers, such as amplifying low-frequency audio or using virtual pitch, face issues like intermodulation distortion and incorrect pitch perception, leading to degraded sound quality.
Innovation Solution
A frequency-domain processing method that estimates the fundamental frequency of the bass signal, translates it to higher frequencies where the speaker is more efficient, and adjusts loudness to maintain the original bass impression, while preserving harmonic structure and avoiding octave errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-frequency audio is amplified to improve bass performance, then bass output is increased, but speaker efficiency deteriorates and energy consumption increases
Solution Approach 1:
The patent changes the frequency parameter of bass signals by translating them to higher frequency ranges (e.g., from 20-200 Hz to 200-2000 Hz) where small speakers operate more efficiently. This frequency translation maintains perceived bass quality through psychoacoustic effects while avoiding the energy inefficiency of direct low-frequency amplification
Solution Approach 2:
The patent replaces the mechanical approach of directly amplifying low-frequency signals with a signal processing approach that uses frequency translation and psychoacoustic principles. Instead of relying on the speaker's mechanical efficiency at low frequencies, the system uses digital signal processing to create virtual bass effects at higher frequencies
2Ease of manufacture
If low-frequency audio is amplified to improve bass performance, then bass output is increased, but speaker reliability deteriorates due to excessive coil excursion
Solution Approach 1:
The patent changes the frequency parameter of bass signals to higher ranges where the speaker coil operates within safe excursion limits. By translating bass frequencies from the problematic 20-200 Hz range to the safer 200-2000 Hz range, the system maintains bass perception while preventing excessive coil movement that causes distortion and damage
Solution Approach 2:
The patent applies preliminary frequency translation to bass signals before they reach the speaker, preventing the harmful effect of excessive coil excursion. By pre-processing the signal to shift frequencies to a safer range, the system proactively avoids the reliability issues that would otherwise occur during bass playback
3Ease of manufacture
If nonlinear devices are used to generate harmonics for virtual bass, then bass perception is improved, but intermodulation distortion increases and degrades audio quality
Solution Approach 1:
The patent replaces the use of nonlinear devices for harmonic generation with a linear frequency translation approach. Instead of using nonlinear distortion to create harmonics, the system uses frequency shifting techniques that translate bass frequencies to higher ranges while maintaining signal fidelity and avoiding intermodulation distortion
Solution Approach 2:
The patent introduces frequency translation as an intermediary process between the original bass signal and the speaker output. This intermediary step transforms the signal to a frequency range where the speaker can reproduce it accurately without requiring nonlinear distortion, thereby eliminating the harmful intermodulation distortion that would otherwise be generated
4Use of energy by moving object
If frequency translation is applied to bass signals, then speaker efficiency is improved, but pitch perception accuracy may deteriorate
Solution Approach 1:
The patent applies frequency translation to shift bass signals to higher frequency ranges where speakers operate more efficiently. By carefully managing the translation process and using psychoacoustic principles, the system maintains accurate pitch perception despite the frequency shift, as the translated frequencies preserve the harmonic relationships and temporal characteristics of the original bass signals
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 balanced bass enhancement, reducing distortion and maintaining sound quality by translating the bass signal to efficient frequency ranges and adjusting loudness, thus improving the overall audio experience.
Implementation Method 1
a frequency translation module to translate the fundamental frequency and harmonics of the bass signal to frequencies at which the loudspeaker can efficiently produce sound
Implementation Method 2
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
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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 in the time domain; (b) a bass extraction filter that extracts a bass portion of the original audio signal, which also is in the time domain; (c) an estimator that estimates a fundamental frequency of a bass sound within the 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; (e) an adder having (i) inputs coupled to the original audio signal and to the virtual bass signal and (ii) an output; and (f) an audio output device coupled to the output of the adder.