Loudspeaker System FIR Filter Direct Sound Attenuation
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Solution Overview
Problem
Conventional surround sound systems are costly, complex, and require additional loudspeakers behind the listener, leading to a reduced spatial sound experience due to direct sound interference, which complicates the creation of a wide sweet spot.
Innovation Solution
A loudspeaker system utilizing FIR filters and delay elements to attenuate direct sound by adjusting the output signals of non-frontal speakers, ensuring effective cancellation of direct sound through destructive interference, without the need for directive loudspeakers or additional speakers behind the listener.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional loudspeakers are placed behind the listener to create surround sound, then the spatial sound experience is improved, but the system cost and complexity increase
Solution Approach 1:
The patent converts the harmful direct sound from lateral loudspeakers into a beneficial component by using it as a reference signal for adaptive filtering. The direct sound, which normally degrades surround sound quality, is instead used to generate cancellation signals that eliminate it, turning a system limitation into a solution enabler.
Solution Approach 2:
The patent introduces adaptive filters as intermediary components between the lateral loudspeakers and the listening position. These filters process the audio signals to generate cancellation components that eliminate direct sound, acting as mediators that resolve the conflict between simple speaker placement and high-quality surround sound.
2Volume of moving object
If lateral loudspeakers are used to create reflections, then the system compactness is improved, but direct sound interference increases
Solution Approach 1:
The patent implements feedback mechanisms where the audio output from lateral loudspeakers is continuously monitored and processed through adaptive filters. The filter coefficients are dynamically adjusted based on the measured or estimated direct sound characteristics, creating a closed-loop system that actively cancels harmful direct sound while maintaining compact speaker placement.
Solution Approach 2:
The direct sound from compact lateral loudspeakers, which is normally harmful, is converted into a useful reference signal for the adaptive filtering process. By using the direct sound path as the basis for generating cancellation signals, the system turns its own limitation into the foundation of its solution.
3Object-generated harmful factors
If directive loudspeakers are used to reduce direct sound, then the direct sound attenuation is improved, but the sweet spot width decreases
Solution Approach 1:
The patent creates virtual copies of the audio signals through adaptive filtering and signal processing. Instead of relying on physical directive loudspeakers with narrow beams, the system generates virtual sound fields that can be precisely controlled and positioned, effectively copying the desired sound distribution pattern without the physical constraints of directive hardware.
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 results in a compact, inexpensive, and flexible surround sound system with a wide sweet spot, effectively eliminating direct sound interference and enhancing the spatial sound experience.
Implementation Method 1
a signal adapted by an FIR filter is emitted for each surround sound channel by at least one front loudspeaker. The timing of the surround sound signal is adjusted by at least one delay signal. In the listening area, the direct sound and the adapted signal meet, thus attenuating the direct sound.
Data Source
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AI summary
The invention relates to a loudspeaker system in which a channel emitted to the side and/or to the ceiling and multiple channels are used in order to provide a surround sound experience in the audience area by means of reflection from walls and/or ceilings. These are what are known as the surround sound channels, which are produced by loudspeakers that do not emit at the front. Undesirable output signals are also produced in this case, what is known as direct sound, which enters the audience area directly, without reflections, and disturbs the surround sound experience. To attenuate the undesirable direct sound, a signal appropriately adapted by an FIR filter is transmitted for each surround sound channel by at least one front loudspeaker. The production of a surround sound signal over time is adapted by at least one delay element in this case. In an audience area, direct sound and the adapted signal now meet one another, which means that the direct sound is attenuated. In comparison with the systems known from the prior art, undesirable direct sound is attenuated effectively and simply by using at least one finite impulse response filter (FIR filter) and at least one delay element. The invention additionally relates to a method for attenuating direct sound and for determining filter functions for attenuating direct sound.