Alternating Pitch Shift for Microphonic Feedback Suppression
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Solution Overview
Problem
Current radio receivers experience microphonic feedback issues due to acoustic vibrations caused by high audio speakers, leading to unstable behavior and a 'howling' effect, which existing mechanical solutions cannot fully mitigate without reducing volume gain.
Innovation Solution
Implementing an alternating pitch shifting method that continuously shifts the pitch of audio signals between positive and negative shifts to prevent regenerative audio feedback, decoupling vibrations from RF components and maintaining volume levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high audio speaker output is increased to provide higher volume levels, then audio loudness is improved, but microphonic feedback and howling effect occur due to acoustic vibrations affecting RF components
Solution Approach 1:
The patent replaces mechanical isolation solutions (padding, ribs, clips) with an electronic/digital solution - alternating pitch shifting of the audio signal. Instead of physically preventing vibrations from reaching RF components, the system digitally modifies the audio signal to prevent regenerative feedback, thereby maintaining high volume levels without howling.
Solution Approach 2:
The patent changes the frequency parameter of the audio signal by applying alternating pitch shifts. This modifies the acoustic characteristics of the signal in a way that prevents synchronization with RF component vibrations, eliminating the regenerative feedback loop while preserving overall audio loudness.
2Stability of the object's composition
If mechanical isolation solutions (padding, ribs, clips) are implemented to prevent board bending, then structural stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent eliminates complex mechanical isolation structures (padding, ribs, clips) by replacing them with a digital signal processing approach. The alternating pitch shifting mechanism achieves the same stability goal through electronic means, significantly reducing mechanical complexity and manufacturing difficulty.
3Reliability
If maximum volume level is reduced to meet gain specification margin, then microphonic feedback is suppressed, but overall loudness level decreases below user expectations
Solution Approach 1:
The patent applies alternating pitch shifts to the audio signal, which modifies the frequency characteristics without reducing overall amplitude. This allows the system to maintain high volume levels while preventing the regenerative feedback that occurs at maximum gain, effectively decoupling loudness from feedback susceptibility.
Solution Approach 2:
The alternating pitch shifting applies periodic frequency modulation to the audio signal. This periodic variation in pitch prevents sustained resonance with RF components, suppressing microphonic feedback while allowing continuous operation at high volume levels without reducing overall loudness.
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 suppresses microphonic feedback, maintaining high volume levels without the 'howling' effect, even in small devices, by continuously alternating the pitch of audio signals to prevent vibrational feedback from affecting RF components.
Implementation Method 1
a audio signal processing circuit of the baseband processor alternately pitch shifts the audio signal to repeatedly shift, in time, the original pitch between a positive pitch shift and a negative pitch shift to produce a pitch swing audio signal
Implementation Method 2
The high audio speaker is a transducer which converts electrical audio signals to mechanical movements of a transducer element to produce acoustic signals in the air
Implementation Method 3
The acoustic transducer creates significantly higher pressure levels compared to low level audio transducers... a large amount of force is required to move the air at the diaphragm where the amount of force is a function of the size of the diaphragm and the size of the magnet
Implementation Method 4
The forceful movement of the diaphragm at high audio levels can also push air into and out of the handset creating pressure which results in audio frequency vibrations in the handset device
Data Source
AI summary
A method and apparatus for receiving and playing a signal in a radio receiver to suppress microphonic feedback are provided by alternately pitch shifting a received audio signal. The pitch of the received audio signal is alternately shifted up and then down, repeatedly over successive intervals of the audio signal, to produce a pitch swing signal which is then played over a speaker. The alternating pitch shifting prevents the buildup of regenerative feedback normally caused by acoustic vibrations coupling into the radio receiver.