Signal Processing System for Reliable Audible Alarm Detection
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Solution Overview
Problem
Existing smoke and carbon monoxide detectors often produce audible alert signals that are ineffective in alerting individuals with hearing loss, older adults, children, and intoxicated persons, due to signal drift from regulations, background noise interference, and varying signal intensity, leading to potential safety risks.
Innovation Solution
A signal processing system that detects audible alert signals from smoke and carbon monoxide detectors using digital templates to match audio patterns, generates supplemental alerts, and can operate in the presence of background noise, ensuring high sensitivity and specificity to minimize false negatives and false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pure tone alarm signals (3100-3200 Hz) are used, then the alarm meets regulatory specifications, but the alarm is ineffective for individuals with hearing loss, older adults, children, and intoxicated persons
Solution Approach 1:
The patent changes the frequency parameter of the alarm signal from traditional 3100-3200 Hz pure tones to lower frequencies (e.g., 520 Hz square wave patterns) that are more effective for alerting individuals with hearing loss, older adults, children, and intoxicated persons while maintaining regulatory compliance through supplemental alerting
2Measurement precision
If the detection device uses high sensitivity to detect weak alarm signals, then detection capability improves, but false positive detections increase due to background noise interference
Solution Approach 1:
The system performs preliminary learning during a quiet period before alarm detection to establish a baseline noise profile of the environment. This pre-acquired noise characterization is then used to differentiate actual alarm signals from background noise, enabling high sensitivity detection without increasing false positives
Solution Approach 2:
The system continuously monitors the audio environment and compares detected signals against the learned noise profile, using feedback mechanisms to adjust detection thresholds and distinguish between background noise variations and actual alarm signals
3Area of stationary object
If the detection device is placed far from the alarm source to provide coverage area, then coverage is improved, but the alarm signal intensity weakens by the time it reaches the detection device
Solution Approach 1:
The system detects periodic alarm signal patterns (such as the characteristic 3-beep or 4-beep sequences of smoke and CO detectors) even when the signals are weak due to distance. By recognizing the temporal pattern rather than relying solely on signal strength, the system maintains detection capability across larger coverage areas
4Reliability
If the system uses multiple templates to cover variations in alarm signals, then detection robustness improves, but the complexity of the detection algorithm increases
Solution Approach 1:
The system uses a limited set of templates covering the most common alarm signal variations (smoke detector patterns, CO detector patterns, and noise profiles) rather than attempting to cover every possible variation. This partial approach maintains robustness for typical scenarios while keeping computational complexity manageable
Data Source
AI summary
A signal processing system and associated methods are disclosed for reliably detecting audible alert signals, such as Temporal-3 (or Code-3) and Temporal-4 (or Code-4) alert signals generated by commercially available smoke, fire, and carbon monoxide detectors. The system and methods are capable of detecting audible alert signals of different intensities in the presence of dynamic background environment (e.g., television programming, music, noise, and the like). The system and methods are capable of detecting audible alert signals generated by far away smoke, fire, and carbon monoxide detectors. The signal processing system and methods may, in some embodiments, be incorporated into a bedside or other unit that generates a supplemental alert signal capable of alerting individuals who might not otherwise respond to the alarm condition, such as individuals who are asleep, children, hearing impaired, or intoxicated.