Metal Detector Audio Rendering With Dynamic Range Compression
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Solution Overview
Problem
Metal detectors face challenges in reproducing audio signals with dynamic ranges exceeding human hearing capabilities, leading to discomfort or missed targets due to excessive sound levels or inadequate volume adjustments.
Innovation Solution
The method involves segmenting the detection signal dynamics into portions and applying specific dynamic change rates, followed by logarithmic conversion and local dynamic modifications to generate an audio signal that aligns with human auditory capabilities, allowing weak signals to be audible and strong signals to avoid discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the audio signal dynamically reproduces the full range of electromagnetic detection signals, then detection sensitivity is improved, but user comfort deteriorates due to excessive sound levels
Solution Approach 1:
The patent applies dynamic compression to the audio signal, continuously adjusting the gain based on the instantaneous amplitude of the detection signal. This dynamic processing maintains the full dynamic range information for detection sensitivity while automatically reducing peak amplitudes that would cause user discomfort, resolving the contradiction between faithful signal reproduction and user comfort.
Solution Approach 2:
The patent changes the amplitude parameter of the audio signal through compression processing, transforming the raw detection signal with its full dynamic range into a compressed audio signal with controlled amplitude. This parameter transformation preserves the informational content for detection while modifying the physical characteristic (amplitude) that directly affects user comfort.
2Object-affected harmful factors
If the audio signal amplitude is reduced for comfort, then user comfort is improved, but detection sensitivity deteriorates due to loss of weak signals
Solution Approach 1:
The dynamic compression process continuously monitors the detection signal amplitude and applies gain reduction only when necessary, preserving the full dynamic range information. Weak signals that require high gain for detection are maintained with minimal compression, while only excessive peak amplitudes are reduced, thus maintaining detection sensitivity while improving user comfort.
Solution Approach 2:
The compression system uses feedback from the instantaneous amplitude of the detection signal to control the gain application. This feedback mechanism ensures that compression is applied adaptively based on the actual signal level, preserving weak detection signals while reducing only those amplitudes that would cause user discomfort.
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 enhances the user experience by ensuring weak signals are heard and strong signals do not cause discomfort, providing a more effective and comfortable audio feedback for metal detection.
Implementation Method 1
an alternating magnetic field is emitted continuously and the detection is based on the amplitude and phase variations between the frequency components of the emitted signal and those of the received signal
Implementation Method 2
the components of the electromagnetic signal received by one or more receiving coils arranged close to the transmitting coil
Implementation Method 3
which makes it possible to generate an incident electromagnetic field, and to receive a resulting magnetic field modified by the immediate environment
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
It is proposed to compress the dynamic range of the target detection signal to match the desired dynamic range (60) of the audio signal (81) generated to audibly reproduce this detection signal for the user. This compression ensures that the weakest signals are audible, that the strongest signals do not cause hearing discomfort for the user, and that the volume of intermediate signals can be perceived gradually. This avoids the loss of variations in the detection signal below the audibility threshold (63) and their clipping above a maximum threshold of auditory comfort (64) in the corresponding audio signal (71) that would be generated according to the prior art.