Acoustic Occupancy Sensor Noise Filtering
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Solution Overview
Problem
Existing lighting control systems lack efficient and reliable methods for determining occupancy in spaces, leading to inefficient energy usage and potential false triggers due to background noise or noise sources like ventilation systems.
Innovation Solution
An occupancy sensor system utilizing an acoustic transmitter, receiver, demodulator, variable band-pass filter, and controller to transmit and process acoustic signals, filtering and time-averaging amplitudes across a range of frequencies to accurately determine presence or absence of occupants, while minimizing false positives through quiet and noisy bandwidth zone identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic signals are used to detect occupancy, then occupancy detection capability is provided, but false triggers occur due to background noise or ventilation systems
Solution Approach 1:
The acoustic spectrum is segmented into multiple frequency bands using a polyphase filter bank. Each frequency band is processed independently to identify quiet bandwidth zones that are less susceptible to noise interference from ventilation systems and other background sources, thereby improving occupancy detection accuracy.
Solution Approach 2:
Different frequency bands are assigned different processing characteristics based on their local noise characteristics. Quiet bandwidth zones are identified and weighted differently from noisy zones, allowing the system to adapt to local acoustic conditions and minimize the impact of background noise on occupancy detection.
2Reliability
If acoustic signals are used to detect occupancy, then occupancy detection capability is provided, but energy consumption increases due to continuous monitoring requirements
Solution Approach 1:
The system performs occupancy detection at periodic intervals rather than continuously monitoring. The processor analyzes acoustic signals at scheduled times, updating occupancy status only when changes are detected or at predetermined intervals, thereby reducing energy consumption while maintaining reliable occupancy detection.
Solution Approach 2:
The system automatically adjusts its monitoring behavior based on detected conditions. When occupancy is detected, the system increases monitoring frequency; when the space is unoccupied, monitoring frequency is reduced, allowing the system to self-regulate energy consumption based on actual occupancy needs.
3Object-affected harmful factors
If multiple frequency bands are processed to identify quiet zones, then noise resistance is improved, but device complexity increases
Solution Approach 1:
The acoustic signal is divided into multiple frequency bands using a polyphase filter bank, allowing parallel processing of each band. This segmentation enables the system to identify quiet bandwidth zones more effectively while distributing the processing load across multiple independent channels, managing complexity through modular architecture.
Solution Approach 2:
The system dynamically adjusts processing parameters such as filter bank configuration, bandwidth zone thresholds, and weighting factors based on detected acoustic conditions. This allows the system to optimize noise resistance for different environments while adapting processing complexity to match actual noise levels and occupancy patterns.
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 system effectively determines occupancy with high accuracy, reducing energy wastage and minimizing false triggers by distinguishing between occupant presence and background noise, enabling precise control of lighting systems.
Implementation Method 1
transmit acoustic signals through a defined region, and receive reflected acoustic signals within the defined region
Data Source
AI summary
An acoustic occupancy sensor includes and acoustic transmitter, acoustic receiver, variable bandpass filter and a controller. The acoustic transmitter transmits acoustic signals into a defined region and the acoustic receiver receives acoustic signals from the defined region. The received acoustic signal is converted to an electrical signal. A pre-amplifier amplifies the electrical signal and the electrical signal is digitized. The digitized electrical signal is demodulated by a demodulator to remove the carrier signal. The digitized electrical signal is filtered by a bandpass filter that sweeps up along a range of frequencies and down along a range of frequencies. The amplitudes of the filtered signals are averaged and analyzed to determine the presence or absence of an occupant within the defined region.