# US 10,121,333 B2 · Device with precision frequency stabilized audible alarm circuit

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- Number: US 10,121,333 B2
- Document ID: US10121333B2
- Status: Granted
- Kind: B2
- Application number: 15/727,059
- Filed: 2017-10-06
- Published: 2018-02-01
- Granted: 2018-11-06
- Earliest claimed: 2015-12-30
- Assignees: Google Inc.
- Applicants: Google Inc.
- Inventors: Daniel Adam Warren; Lawrence Frederick Heyl; Dietrich Ho; Morakinyo John Aina; Ian C. Smith; William Saperstein; Bhaskar Vadathavoor
- Web page: https://patentgrep.com/patent/US10121333B2

## CPC

- G08B 3/10: using electric transmission; using electromagnetic transmission
- G08B 29/18: Prevention or correction of operating errors (G08B29/02, G08B29/12 take precedence)
- H04R 17/00: Piezoelectric transducers; Electrostrictive transducers (piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners {H10N30/00})
- H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F)
- H04R 2430/01: Aspects of volume control, not necessarily automatic, in sound systems
- G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

Systems for ensuring an audible alarm circuit sounds at a minimum magnitude of loudness are provided. Different circuitry embodiments discussed herein are each capable of assisting the audible alarm circuit in maintaining a minimum loudness threshold. Audible alarm circuit operation optimization can be achieved using embodiments that fall within anyone of four general categories: compensation networks, direct drive, dynamic tuning, and microphone feedback based dynamic tuning. Use of such circuitry can increase production yields by compensating for manufacturing variations of alarm components and aging characteristics of the components.

## Claims

### Claim 1

A device comprising:
an electroacoustic transducer;
driver circuitry coupled to the transducer, the driver circuitry operative to drive operation of the transducer;
control circuitry coupled to the driver circuitry, the control circuitry operative to provide a signal that can vary output of the driver circuitry;
a microphone;
sense circuitry coupled to the control circuitry and the microphone, the sense circuitry operative to:
monitor an output of the microphone; and
instruct the control circuitry to change a value of its adjustable network based on the monitored output of the microphone such that the transducer emits an audio signal having at least a minimum magnitude, wherein the transducer is coupled to the control circuitry, and wherein the sense circuitry permanently configures the adjustable network to be used as a phase shift network that supplements a phase of the transducer to enable stable operation of the transducer.

### Claim 2 (depends on 1)

The device of claim 1, wherein the sense circuitry instructs the control circuitry in real-time.

### Claim 3 (depends on 1)

The device of claim 1, wherein the control circuitry comprises an adjustable network that can vary output of the driver circuitry, and wherein the sense circuitry instructs the control circuitry to change a value of its adjustable network based on the monitored output of the microphone such that the transducer emits an audio signal having a maximum magnitude.

### Claim 4 (depends on 1)

The device of claim 1, wherein the value is changed such that the stable operation of the transducer at the at least the minimum magnitude occurs at a resonant frequency of about 520 Hz.

### Claim 5 (depends on 1)

The device of claim 1, wherein the value is changed such that the stable operation of the transducer at the at least the minimum magnitude occurs at a resonant frequency of about 3 kHz.