Ultrasonic Beam Localization for Private Audio Fields
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Solution Overview
Problem
Conventional techniques for generating localized sound fields are limited by the size of acoustic transducer systems and struggle to produce focused sound near a target location without residual audible sound, leading to issues like loss of privacy and unwanted disturbance.
Innovation Solution
The technique employs a system with primary and corrective ultrasonic beams to create a localized audible sound field by destructive interference, ensuring sufficient sound pressure at the target location while suppressing residual sound outside the designated area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional acoustical wave theory is used to manipulate audible sound waves, then sound can be directed to particular regions, but the transducer system size becomes large and residual sound occurs outside the target area
Solution Approach 1:
The patent replaces conventional audible sound wave manipulation with ultrasonic wave manipulation. By using ultrasonic frequencies (above human hearing range) and exploiting non-linear air-borne modulation, the system achieves sound field localization without the limitations of conventional acoustical wave theory, eliminating residual audible sound outside the target region
Solution Approach 2:
The patent changes the frequency parameter from audible sound waves to ultrasonic waves. This parameter change enables the use of non-linear air-borne ultrasound modulation techniques, which create localized audible sound fields through demodulation in the air medium, thereby reducing transducer size and eliminating residual sound leakage
2Power
If non-linear air-borne ultrasound modulation is used to generate directional audio beams, then sound pressure level is maintained along the beam direction, but the beam width remains relatively narrow and positioning precision is limited
Solution Approach 1:
The patent divides the ultrasonic transmission into multiple frequency components (carrier frequency and modulation frequencies) that can be independently controlled and focused. This segmentation allows precise positioning of the demodulated audible sound field while maintaining adequate sound pressure level through constructive interference at the target location
Solution Approach 2:
The patent applies preliminary focusing to the ultrasonic beams before they propagate through the air medium. By pre-positioning the focal points of the ultrasonic carrier and modulation waves, the system ensures that demodulation occurs at the desired spatial location, achieving both sufficient sound pressure level and precise positioning
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 enables the generation of a localized sound field with sufficient sound pressure (at least 60-70 dB) at the target spot while significantly reducing residual sounds, maintaining privacy and minimizing unwanted disturbances.
Implementation Method 1
Technologies utilizing the so called non-linear air-borne ultrasound modulation for generation of audible sound. These techniques manipulate the frequency content of non-audible ultrasonic (US) waves (i.e. sound waves of relatively short wavelengths) and rely on the non-linearity of the sound propagation medium (e.g. air/water) for the generation of audible sound from the short ultrasonic waves.
Implementation Method 2
According to one of these approaches, a directional audio beam demodulates from high frequency ultrasound waves at high sound pressure level (SPL).
Implementation Method 3
The phenomena of air (and water) non-linear medium behavior under high SPL sound wave transmission was discovered 45 years ago when experimenting on sonar waves for submarines. This effect is described mathematically by the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation which describes the propagation of waves in space in consideration of waves interference, waves dispersion and non-linear response of the medium (e.g. air) through which the waves propagate.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E~1G
AI summary
A system and method are presented for generating a localized audible sound field at a designated spatial location. The method comprises: providing sound-data indicative of an audible sound to be produced and location-data indicative of a designated spatial location at which the audible sound is to be produced; and utilizing the sound-data and determining frequency content of at least two ultrasound beams to be transmitted by an acoustic transducer system including an arrangement of a plurality of ultrasound transducer elements for generating said audible sound. The at least two ultrasound beams include at least one primary audio modulated ultrasound beam, whose frequency contents includes at least two ultrasonic frequency components selected to produce the audible sound after undergoing non-linear interaction in a non linear medium, and one or more additional ultrasound beams each including one or more ultrasonic frequency components. The location-data is utilized for determining at least two focal points for the at least two ultrasound beams respectively such that focusing the at least two ultrasound beams on the at least two focal points enables generation of a localized sound field with the audible sound in the vicinity of the designated spatial location.