MEMS Speaker Architecture Using Ultrasonic Modulation for Compact Sound

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Solution Overview

Problem

Portable devices with low-profile transducers face challenges in maintaining optimal sound quality due to their compact size, which affects the efficiency of sound generation and transmission.

Innovation Solution

A microelectromechanical systems (MEMS) speaker architecture utilizing ultrasonic modulation and demodulation techniques, incorporating chip-scale unit cells with cantilever beams or pistonic actuators formed from MEMS materials, to generate audible sound through ultrasonic carrier and modulator frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the transducer profile is reduced to fit portable devices, then the device compactness is improved, but the sound quality deteriorates

Engineering Contradiction:

Improvetransducer volumeVSAvoidsound quality

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the operating parameters by using ultrasonic frequencies (above 20kHz) for the carrier wave and modulating it with audible frequency signals. This parameter change allows the transducer to generate audible sound through nonlinear air interaction rather than direct acoustic radiation, enabling high sound quality in a compact form factor

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional mechanical acoustic radiation system with an electrostatic or piezoelectric actuation system that generates ultrasonic vibrations. These ultrasonic vibrations interact with air nonlinearities to produce audible sound, substituting direct mechanical sound generation with a field-based approach that works effectively at small scales

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If ultrasonic modulation is used to generate audible sound, then the sound directivity is improved, but the device complexity increases

Engineering Contradiction:

Improvesound directivityVSAvoidtransducer structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent merges the carrier beam generator and modulator beam generator into a single integrated MEMS transducer unit. The modulator beam is positioned to interact with the carrier beam in the air gap, combining multiple functions (ultrasonic generation, modulation, and acoustic radiation) into one compact structure rather than separate components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses out-of-plane movement of the modulator beam relative to the carrier beam to achieve modulation. By moving in the vertical dimension (perpendicular to the sound radiation direction), the modulator can vary the effective aperture and interaction volume with the carrier beam, enabling amplitude modulation that produces audible sound with improved directivity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 MEMS speaker architecture enhances sound directivity and quality, particularly at low frequencies, by leveraging ultrasonic modulation to produce improved acoustic output in a compact form factor.

Implementation Method 1

a first sound radiating member operable to produce a first frequency... the first frequency comprises a carrier frequency within an ultrasonic frequency range

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 2

The actuation of the beams or pistonic actuators may be electrostatic or piezoelectric

Methodology Applied

Scientific EffectElectrostatic actuation: Electrostatics

Implementation Method 3

at least one of the first sound radiating member or the second sound radiating member comprises a piezoelectric beam

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 4

a second sound radiating member arranged parallel to the first radiating member and operable to produce a second frequency... the second frequency comprises a modulator frequency

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 5

uses ultrasonic modulation and demodulation techniques to generate audible sound. Ultrasonic modulation and demodulation speaker techniques generate an audible sound from modulated ultrasound using an amplitude-modulated ultrasonic wave

Methodology Applied

Scientific EffectAcoustic modulation and demodulation:

Implementation Method 6

create audible sound in air using ultrasound and the non-linearity of air

Methodology Applied

Scientific EffectNonlinear acoustic interaction:

Data Source

PatentUS20250287139A1MEMS Speaker Architecture

Publication Date: 2025.09.11 APPLE INC

AI summary

A microelectromechanical transducer assembly comprising: an enclosure defining an interior chamber and an opening from the interior chamber to a surrounding ambient environment; a first sound radiating member operable to produce a first frequency; and a second sound radiating member arranged parallel to the first radiating member and operable to produce a second frequency that in combination with the first frequency generates an audible sound output.