Acoustic Distance Measurement Using Cross-Correlation
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Solution Overview
Problem
Mobile communication devices face challenges in measuring distances efficiently due to power consumption and processing requirements, as existing methods often necessitate additional components and significant resources.
Innovation Solution
A method utilizing a standard microphone and speaker to emit and process ultrasound signals, which reduces processing needs and power consumption by employing acoustic reference signals with good auto-correlation properties, allowing for accurate distance measurement without dedicated hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional components are used for distance measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the existing speaker and microphone for both audio communication and distance measurement. The speaker emits acoustic reference signals in addition to audio content, while the microphone captures both audio input and reflected acoustic signals. This allows the same hardware components to serve dual purposes, eliminating the need for dedicated distance measurement hardware.
Solution Approach 2:
The device uses its own existing audio components (speaker and microphone) to perform distance measurement, rather than requiring external or dedicated sensors. The system essentially measures distance using itself as both the signal source and the detector, leveraging already-present hardware to solve the measurement problem without adding specialized components.
2Measurement precision
If significant processing resources are allocated to distance measurement, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent extracts and analyzes only the specific portion of the microphone signal that corresponds to the reflected acoustic reference signal. By identifying and isolating the measurement portion through correlation analysis, the system processes only the relevant data rather than analyzing the entire audio signal stream, thereby reducing computational load and power consumption while maintaining measurement accuracy.
Solution Approach 2:
The system performs partial processing by focusing computational resources only on the necessary signal analysis for distance measurement. Instead of processing the complete audio signal, it applies correlation techniques specifically to identify and measure the reflected reference signal portion, achieving sufficient measurement precision with reduced processing effort.
3Ease of operation
If acoustic reference signal is emitted simultaneously with audio signal, then ease of operation is improved, but signal interference increases
Solution Approach 1:
The patent uses signal processing techniques where the known acoustic reference signal acts as an intermediary for extracting measurement information from the mixed signal. By cross-correlating the received signal with the known reference signal, the system can identify and isolate the reflected reference signal portion even when mixed with audio content, effectively separating the measurement signal from the audio signal through mathematical processing.
Solution Approach 2:
The system maintains continuous operation by emitting the acoustic reference signal continuously or periodically alongside audio signals without interruption. This allows distance measurement to occur simultaneously with normal audio communication, ensuring that the measurement function operates continuously without requiring separate measurement phases or interrupting audio playback.
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 accurate distance measurement with low power consumption and minimal processing requirements, allowing for simultaneous use during voice communications and other device functions, while being adaptable to various objects and distances.
Implementation Method 1
a first acoustic reference signal is emitted by a speaker of the device... an acoustic input signal is received at a microphone of the device... extracting a section of the cross correlated signal corresponding to reflection of the acoustic reference signal by the object
Implementation Method 2
A method utilizing a standard microphone and speaker to emit and process ultrasound signals
Implementation Method 3
analysing the extracted section of the cross correlated signal to determine a time of flight... determining the time difference between the time of the centre of gravity and a first time at which the acoustic reference signal was emitted
Data Source
AI summary
A method for determining a distance between a device and an object, the method comprising: emitting an acoustic reference signal from a speaker of the device; receiving an acoustic input signal at a microphone of the device, the acoustic input signal including a measurement portion including a reflection of the acoustic reference signal off the object; cross correlating at least the measurement portion with the emitted acoustic reference signal to provide a cross correlated signal; receiving information relating to the object; extracting a section of the cross correlated signal corresponding to reflection of the acoustic reference signal by the object, based on the received information; analyzing the extracted section of the cross correlated signal to determine a time of flight between emitting the acoustic reference signal and receiving the reflection; and determining the distance between the device and the object based on the determined time of flight and known characteristics of the acoustic reference signal. A chipset for performing the method is also disclosed.