Parametric Sound Transducer Bass Response

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Solution Overview

Problem

Parametric sound systems face limitations in bass response and maximum achievable volume due to the natural high-pass filtering effect of the demodulation process, making them unsuitable for applications requiring high volume sound reproduction and unable to compete with Hi-Fi/Hi-End systems.

Innovation Solution

The method involves adaptive frequency filtering and square root operation to invert the non-linear demodulation process, amplifying the modulated ultrasonic signal with a series-resonant circuit using a high-frequency coil, and employing electrostatic transducers with a specific back plate structure that allows for phased array control and improved electromechanical efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If equalizer is applied to flatten frequency response, then bass response is improved, but overall sound volume is diminished

Engineering Contradiction:

Improvefrequency responseVSAvoidoverall sound volume

Core Design Contradiction:

ShapeVSPower

Solution Approach 1:

The patent applies preliminary action by preprocessing the audio signal with integration before modulation. This advance processing compensates for the high-pass filtering effect that will occur during demodulation, ensuring bass frequencies are restored without requiring post-processing equalization that would reduce overall volume.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes parameters by applying integration to the audio signal, which transforms the frequency content to preemptively counteract the demodulation high-pass effect. This parameter transformation allows bass enhancement without the volume loss associated with traditional equalization approaches.

Inventive Principle:

Principle #35Parameter changes

2Power

If large amplitude ultrasonic waves are used to increase sound volume, then bass response is improved, but human exposure safety limit is exceeded

Engineering Contradiction:

Improvesound volumeVSAvoidultrasonic exposure safety

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The integration preprocessing is applied in advance to the audio signal, which allows the system to achieve bass enhancement without needing to increase ultrasonic amplitude beyond safety limits. The mathematical transformation prepares the signal so that demodulation produces the desired bass response at safe exposure levels.

Inventive Principle:

Principle #10Preliminary action

3Power

If piezoelectric transducers are used to achieve high output pressure levels, then sound volume is improved, but bandwidth is reduced and system cost increases

Engineering Contradiction:

Improveoutput pressure levelVSAvoidfrequency bandwidth

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical piezoelectric transducer system with an electrostatic transducer system. This substitution maintains high output pressure capability while achieving superior bandwidth performance, as electrostatic transducers can operate effectively across a wider frequency range including the ultrasonic frequencies required for parametric sound generation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 bass performance, maximizes the volume of reproduced sound within safe ultrasound pressure limits, and enables the manufacture of low-cost, customizable transducers with improved efficiency and phased array capabilities.

Implementation Method 1

When a DC biased electrical signal is applied between membrane and the back plate, the membrane moves towards or away from the back plate due to electrostatic forces

Methodology Applied

Scientific EffectElectrostatic forces: Electrostatics

Implementation Method 2

amplifying the modulated ultrasonic signal with a series-resonant circuit using a high-frequency coil

Methodology Applied

Scientific EffectSeries-resonance: Resonance

Implementation Method 3

Parametric sound is produced when ultrasonic waves modulated with audio signal demodulate while travelling in air

Methodology Applied

Scientific EffectNon-linear demodulation:

Data Source

PatentUS11735155B2Method for generating parametric sound and means for carying out said method

Publication Date: 2023.08.22 UAB NEUROTECH

AI summary

The present invention discloses a method for producing parametric sound using parametric sound system which is based on ultrasonic electrostatic transducers. It comprises modulation of a carrier ultrasonic signal with a processed audio signal in audio signal processor comprising adaptive frequency filtering based on the audio signal level, dynamic range compression, square root operation, amplification of the modulated ultrasonic signal using a D-class amplifier, driving an electrostatic transducer and generating modulated ultrasonic waves into the air. The electrostatic transducer for the parametric sound system comprises a specific back plate structure that improves electromechanical efficiency of the transducer and also enables realization of a phased array on a single back plate. The disclosed manufacturing method of the electrostatic transducer comprises producing sets of electrodes on the surface of the back plate forming individual cells.