Parametric Loudspeaker Sound Pressure Control
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Solution Overview
Problem
Existing acoustic apparatuses with super-directivity using parametric loudspeakers struggle to maintain sufficient sound pressure in the listening area while effectively canceling sound pressure in the non-listening area, as the cancellation of sound pressure is excessive in both areas.
Innovation Solution
An acoustic apparatus comprising an amplitude modulation unit, a phase control unit, a first parametric loudspeaker, a reflection unit, and a second parametric loudspeaker, where the amplitude modulation unit generates signals with different sound pressure distributions, and the phase control unit adjusts phases to create interference, allowing for precise control of the sound pressure distribution to separate listening and non-listening areas by focusing sound waves at a control point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If sound waves from two parametric loudspeakers are interfered to cancel sound pressure at the non-listening area, then sound pressure separation between listening and non-listening areas is improved, but sound pressure at the listening area is excessively reduced
Solution Approach 1:
The patent applies local quality by creating different sound pressure characteristics in different spatial regions. The first sound wave is designed to have high sound pressure at the listening area, while the second sound wave (reflected by the concave) is designed to have high sound pressure at the non-listening area. This spatial differentiation of sound pressure characteristics allows selective cancellation: at the non-listening area, the two waves cancel each other, while at the listening area, the first wave dominates and maintains sufficient sound pressure.
Solution Approach 2:
The concave structure serves as an intermediary element that transforms the sound wave propagation characteristics. By reflecting the second sound wave, the concave creates a focal point at the non-listening area, enabling the second wave to have high sound pressure there. This intermediary structure is key to achieving the desired sound pressure distribution without directly affecting the listening area.
2Object-affected harmful factors
If sound pressure cancellation is applied in both listening and non-listening areas, then sound pressure separation is achieved, but sound pressure in the listening area cannot be sufficiently maintained
Solution Approach 1:
The patent implements local quality by ensuring that sound pressure cancellation occurs only at the non-listening area while preserving sound pressure at the listening area. This is achieved by designing the first sound wave to have high sound pressure at the listening area and the second sound wave (reflected by the concave) to have high sound pressure at the non-listening area, creating spatially differentiated sound pressure characteristics that enable selective cancellation.
Solution Approach 2:
The patent segments the sound field into distinct listening and non-listening areas with different sound pressure characteristics. By using two separate parametric loudspeakers emitting sound waves with different spatial distributions, the system divides the acoustic space into regions with different properties, allowing independent control of sound pressure in each region.
3Object-affected harmful factors
If two parametric loudspeakers with identical sound pressure distribution are used for interference, then sound pressure cancellation at non-listening area is achieved, but sound pressure distribution becomes uniform and cannot maintain sufficient pressure at listening area
Solution Approach 1:
The patent applies local quality by creating different sound pressure characteristics in different spatial regions. The first sound wave is designed to have high sound pressure at the listening area, while the second sound wave (reflected by the concave) is designed to have high sound pressure at the non-listening area. This spatial differentiation of sound pressure characteristics allows selective cancellation: at the non-listening area, the two waves cancel each other, while at the listening area, the first wave dominates and maintains sufficient sound pressure.
Solution Approach 2:
The patent employs asymmetry by using a concave structure to reflect the second sound wave, creating an asymmetric sound pressure distribution. The concave focuses the second wave at a specific point (non-listening area) while leaving the listening area with different characteristics. This asymmetric approach enables the system to achieve cancellation at the non-listening area without uniformly reducing sound pressure throughout the entire space.
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
The apparatus effectively maintains sound pressure in the listening area and attenuates it steeply in the non-listening area, clearly separating the two regions by utilizing the unique sound pressure distribution characteristics of the interfering sound waves.
Implementation Method 1
a first parametric loudspeaker to radiate a first sound wave toward a first control point, based on the second signal
Implementation Method 2
The first reflection unit has a first concave to receive a sound wave and reflect the sound wave toward the first control point
Implementation Method 3
the phase control unit is configured to generate a second signal and a third signal by controlling a phase of the first signal. Respective phases of the second signal and the third signal are approximately opposite
Data Source
AI summary
According to one embodiment, an amplitude modulation unit generates a first signal by modulating an amplitude of a carrier wave signal having a frequency of an ultrasonic band, based on an acoustic signal. A phase control unit generates a second signal and a third signal by controlling a phase of the first signal. Respective phases of the second signal and the third signal are approximately opposite. A first parametric loudspeaker radiates a first sound wave toward a first control point, based on the second signal. A first reflection unit has a first concave to receive a sound wave and reflect the sound wave toward the first control point. A focal point of the sound wave reflected by the first concave is the first control point. A second parametric loudspeaker radiates a second sound wave toward the first concave, based on the third signal.