Acoustic Reflection for Opaque Display Sound Alignment
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Solution Overview
Problem
Light emissive screens in cinemas and other large screen applications are not transparent to sound, causing a disassociation between sound and image, particularly for center channel sound, and existing de-elevation techniques are ineffective and rely on heavy signal processing.
Innovation Solution
A system using two separate sound sources, a high frequency loudspeaker positioned in front of and angled towards the screen to reflect high frequency sound, and a low frequency loudspeaker positioned at or near the screen to provide direct low frequency sound, with a cross-over between 350 to 1000 Hz and signal delay to time-align the sound components, ensuring full-bandwidth sound appears to come from the image screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If loudspeakers are positioned behind the emissive screen, then center channel sound is achieved, but the screen must be transparent to sound which light emissive screens are not
Solution Approach 1:
The sound delivery system is segmented into two separate loudspeakers: one positioned behind the screen for center channel sound and another positioned in front of the screen for high-frequency content. This segmentation allows each loudspeaker to fulfill specific acoustic requirements that a single behind-screen loudspeaker cannot satisfy with opaque screens.
Solution Approach 2:
The emissive screen itself acts as an intermediary element that partially transmits low-frequency sound from behind-screen loudspeakers while reflecting high-frequency sound from front-screen loudspeakers. This intermediary role of the screen enables the system to overcome its opacity limitation by utilizing its reflective properties for high frequencies.
2Reliability
If loudspeakers are positioned above the emissive screen, then sound delivery is achieved, but the sound appears to come from an elevated position causing disassociation between sound and image
Solution Approach 1:
The audio spectrum is segmented into low-frequency and high-frequency components, delivered by separate loudspeakers positioned at different locations. Low frequencies from the behind-screen loudspeaker maintain spatial association with the image, while high frequencies from the front-screen loudspeaker are reflected to supplement clarity without creating elevation perception.
Solution Approach 2:
Different parts of the sound spectrum are handled with different local qualities: low-frequency sound is allowed to pass through the screen to maintain image association, while high-frequency sound is reflected from the front to enhance clarity. This local quality differentiation resolves the spatial disassociation problem.
3Loss of information
If de-elevation techniques are used to make elevated sound appear to come from the screen, then spatial association is attempted, but the technique relies on heavy signal processing and is largely ineffective
Solution Approach 1:
The patent replaces the complex digital signal processing system (de-elevation filters) with a simpler acoustic solution using separate physical loudspeakers positioned strategically. The acoustic reflection and transmission properties of the screen substitute for the complex electronic processing, achieving spatial association more effectively with less complexity.
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 solution effectively associates full-bandwidth sound with images on acoustically reflective screens without relying on de-elevation techniques, providing a cohesive audio experience by ensuring high frequency sound is reflected and low frequency sound is direct, thus maintaining the illusion of sound originating from the screen.
Implementation Method 1
the high frequency components of the sound associated with the images displayed on the acoustically reflective image screen are directed at the image screen such that high frequency components of the sound arrive at the audience as reflected sound only
Implementation Method 2
low frequency components of the sound associated with the images on the image screen are directed at the audience such that the low frequency components of the sound arrive at the audience not as reflected sound but as direct sound
Data Source
AI summary
A system and method for delivering full-bandwidth sound to an audience in an audience space located in front of an acoustically reflective image screen such as a plasma, LCD, LED, or OLED screen. The sound delivery system provides for two separate and spatially displaced sound sources, namely, a high frequency loudspeaker for reproducing high frequency components of the sound associated with images displayed on the acoustically reflective image screen, and a separate low frequency loudspeaker for reproducing low frequency components of the image-associated sound. The high frequency loudspeaker or loudspeakers are positioned in front of the image screen to direct the high frequency components of the sound at the image screen where it is reflected back into the audience space, whereas the low frequency loudspeaker or loudspeakers are positioned at or about the acoustically reflective image screen and direct the low frequency components of the sound toward the audience space which are time-aligned with the high frequency components.