Ultrasonic Recording Prevention via Frequency Modulation
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Solution Overview
Problem
Conventional methods for preventing recording in electronic devices with microphones using ultrasound are ineffective due to the generation of shadow regions and require complex circuit structures, leading to user inconvenience and reduced recording prevention efficiency.
Innovation Solution
A system that generates a complex recording prevention signal using a simple circuit structure, including a control unit, modulation units, and an ultrasonic output unit with adjustable frequency and amplitude, along with an air blower for Doppler effect modulation, to minimize shadow regions and prevent recording without straining users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-tone ultrasonic signal is used to prevent recording, then the circuit structure remains simple, but shadow regions are generated and recording prevention effectiveness is reduced
Solution Approach 1:
The patent applies periodic action by modulating the ultrasonic signal with audio frequency signals, creating a time-varying complex ultrasonic signal. This modulation causes the ultrasonic signal to periodically change in frequency and amplitude, which prevents the formation of stable shadow regions while maintaining circuit simplicity through standard modulation techniques.
Solution Approach 2:
The patent implements dynamics by making the ultrasonic signal dynamic rather than static. The frequency and amplitude of the ultrasonic signal are dynamically adjusted through modulation with audio signals, allowing the signal characteristics to change over time and space, thereby eliminating shadow regions without requiring complex circuit architecture.
2Reliability
If ultrasound frequency is changed to eliminate shadow regions, then recording prevention effectiveness improves, but ultrasonic output power decreases due to transducer resonant frequency characteristics
Solution Approach 1:
The patent applies parameter changes by modulating the ultrasonic signal parameters (frequency and amplitude) with audio frequency signals. This allows the ultrasonic frequency to vary around the transducer's resonant frequency rather than being fixed, maintaining high output power while still preventing shadow region formation through frequency variation.
Solution Approach 2:
By using periodic modulation of the ultrasonic signal at audio frequencies, the patent enables the ultrasonic frequency to periodically sweep through a range centered on the resonant frequency. This periodic variation maintains average power output while eliminating shadow regions, resolving the contradiction between effectiveness and power.
3Reliability
If strong ultrasonic signal is radiated to ensure recording prevention, then recording prevention effectiveness improves, but user comfort deteriorates due to hearing strain and fatigue
Solution Approach 1:
The patent applies local quality by directing the strong ultrasonic signal specifically toward the microphone of the electronic device rather than radiating it uniformly in all directions. The modulated ultrasonic signal is focused locally at the target microphone, ensuring effective recording prevention at the specific location while minimizing exposure to users in the surrounding environment.
Solution Approach 2:
The periodic modulation of the ultrasonic signal creates a time-varying pattern that is less likely to cause continuous hearing strain compared to a constant strong signal. The audio-frequency modulation allows the signal to vary in intensity, reducing the cumulative effect on user hearing while maintaining effectiveness at the target microphone through constructive interference.
4Device complexity
If conventional ultrasonic recording prevention is used, then the circuit structure remains simple, but the method becomes ineffective when a filter blocks inaudible signals at the microphone input
Solution Approach 1:
The patent applies parameter changes by modulating the ultrasonic signal with audio frequency components, creating a complex signal with varying frequency and amplitude characteristics. This modulation transforms the signal parameters so that it can potentially penetrate or bypass frequency-based filters that block simple inaudible ultrasonic tones, while still using relatively simple modulation circuitry.
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
Effectively prevents recording in electronic devices while minimizing shadow regions and maintaining user convenience by generating a complex noise signal that is inaudible and efficient, thus preventing unauthorized recording.
Implementation Method 1
an ultrasound output unit for converting an electrical signal into an ultrasonic signal using the transducer and radiating a recording prevention signal
Implementation Method 2
a resonance unit for generating resonance and thereby increasing the voltage to be applied to a transducer
Implementation Method 3
an air blower unit for generating airflow near the microphone of the electronic device in order to modulate the recording prevention signal
Data Source
AI summary
An apparatus and method for preventing an electronic device from recording. The apparatus includes a control unit for generating a first modulation signal and controlling the components of the apparatus; a first modulation unit for modulating the first modulation signal to an FM signal; an ultrasonic signal generation unit for generating an ultrasonic signal, the frequency of which is adjusted by changing the value of at least one of a variable resistor and a variable capacitor depending on the magnitude of the FM signal; an amplification unit for increasing or decreasing the magnitude of the ultrasonic signal; a resonance unit for increasing the voltage to be applied to a transducer by generating resonance; and an ultrasound output unit for converting electrical signals into ultrasonic signals using the transducer and radiating a recording prevention signal, converted into the ultrasonic signal, to the microphone of an electronic device.