Parametric Loudspeaker Reflector With Ultrasonic Absorption
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Solution Overview
Problem
Existing parametric loudspeaker technologies face issues with low audible sound levels relative to ultrasonic wave levels, excessive ultrasonic wave radiation to users, and undesirable audible sound reproduction at reflection destinations.
Innovation Solution
An acoustic system incorporating a parametric loudspeaker with a reflector and sound absorber to collect and amplify audible sound while attenuating ultrasonic waves, using a paraboloid of revolution reflector and phononic crystal or closed resonance tubes to absorb ultrasonic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflector is provided to collect the ultrasonic wave radiated from the parametric loudspeaker, then the level of audible sound reproduction is increased, but the level of ultrasonic wave radiation to the user becomes higher
Solution Approach 1:
The audible sound collector is segmented into two functional zones: a sound absorption portion positioned to absorb ultrasonic waves before they reach the user, and a reflection portion positioned to reflect audible sound waves toward the user. This spatial segmentation allows selective handling of different frequency components, absorbing harmful ultrasonic energy while directing useful audible sound, thereby resolving the contradiction between increasing audible sound level and reducing ultrasonic radiation level
Solution Approach 2:
Different portions of the audible sound collector are assigned different local qualities: the sound absorption portion has acoustic absorption properties optimized for ultrasonic frequencies, while the reflection portion has acoustic reflection properties optimized for audible frequencies. This local quality differentiation enables each portion to perform its specific function effectively, allowing the system to enhance audible sound while mitigating ultrasonic radiation
2Illumination intensity
If a reflector is provided to collect the ultrasonic wave radiated from the parametric loudspeaker, then the level of audible sound reproduction is increased, but audible sound is reproduced at the destination to which the ultrasonic wave is reflected
Solution Approach 1:
The audible sound collector is divided into functionally distinct sound absorption portion and reflection portion. The sound absorption portion is positioned and configured to absorb ultrasonic waves and prevent them from reaching destinations where they would be reflected back as audible sound. The reflection portion is configured to reflect audible sound waves toward the intended listening area. This segmentation prevents the harmful effect of audible sound reproduction at unintended destinations while maintaining enhanced audible sound levels where needed
Solution Approach 2:
The sound absorption portion acts as an intermediary element that intercepts ultrasonic waves before they can be reflected by the reflector surface. By absorbing these ultrasonic waves, it prevents their conversion to audible sound at reflection destinations, thereby eliminating the harmful effect of undesirable audible sound reproduction while allowing the reflection portion to enhance audible sound at the intended location
3Illumination intensity
If the level of ultrasonic wave is increased to improve audible sound reproduction, then the level of audible sound is improved, but the ultrasonic wave of high level is radiated to the user
Solution Approach 1:
The sound absorption portion is designed to extract and remove ultrasonic wave energy from the acoustic field before these waves can reach the user. By selectively absorbing ultrasonic frequencies while allowing audible frequencies to pass and be reflected, it extracts the harmful ultrasonic component from the mixed acoustic signal, enabling high-level audible sound reproduction without corresponding high-level ultrasonic radiation to the user
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
Enhances audible sound reproduction levels while mitigating ultrasonic wave radiation and reflection-related issues, ensuring clear and safe sound collection for users.
Implementation Method 1
radiates an ultrasonic wave by amplitude-modulating an ultrasonic wave signal with an audible sound signal
Implementation Method 2
reproducing the audible sound with a high directivity as an audible sound self-demodulated while the ultrasonic wave propagates in the air
Implementation Method 3
a reflector having a reflecting surface configured to reflect a sound wave that becomes incident thereto in a same direction as a direction in which the emitted sound wave becomes incident thereto
Implementation Method 4
a sound absorber configured to attenuate an ultrasonic wave component of the emitted sound wave reaching the reflecting surface
Implementation Method 5
a sound absorbing material made of a phononic crystal for absorbing an ultrasonic wave
Implementation Method 6
a plurality of closed resonance tubes configured to absorb an ultrasonic wave
Implementation Method 7
driving a high-directivity ultrasonic transducer array by the amplitude-modulated signal, thereby reproducing the audible sound with a high directivity
Data Source
Figure 1
Figure 2A~2G
Figure 3A~3F
AI summary
An acoustic system and an in-vehicle communication support system that increase the audible sound reproduction level of a parametric loudspeaker while mitigating disadvantages of ultrasonic radiation are provided. An ultrasonic wave amplitude-modulated with audible sound, emitted from a parametric loudspeaker enter an audible sound collector with a high directivity. Of incident ultrasonic wave and incident audible sound self-demodulated from the ultrasonic wave, the audible sound collector attenuates the ultrasonic wave, and reflects the audible sound to be collected at a position near the user. The audible sound collector can be composed of: a reflector having a reflecting surface formed of a paraboloid of revolution; and a sound absorber for absorbing an ultrasonic wave. The sound absorber can be composed of a sound absorbing material made of a phononic crystal, or of resonance tubes.