Enhancing signal to noise ratio for electrostatic transducers

This Thesis describes the design, manufacture and evaluation of a Fluidically Amplified Ultrasonic Transducer (FLAUT) for an air-coupled application. The transducer utilises a pipe as an amplification mechanism to increase the output pressure; and as a dissipation mechanism to reduce inherent noise within the transducer. The new transducer design introduces the concept of matched thin plate, cavity and pipe, of which the individual geometry enhances one another. Design methodologies, which consist of analytical modelling and Finite Element (FE) Modelling, have been implemented. The analytical modelling identifies the required geometry for the FLAUT based on the desired operating resonant frequency; while FE then verifies the vibrational characteristics of the design. Through the application of FE modelling and practical analysis, FLAUT devices have been designed, developed and compared with experiment. The sensitivity analysis is utilised to realise a design and manufacturing tolerance requirements. The devices were manufactured in the operating range of 25 kHz to 85 kHz. Air-coupled pulse-echo insertion loss was found to be 61.3 dB, an improvement of 9.1 dB over the conventional cavity only design. Results from the proof of concept prototype indicate that the output of the FLAUT is maximised when the pipe radius is designed to be as large as practically possible while maintaining the matched resonant frequencies. This correlates well with theory both in term of sensitivity and noise. Furthermore, the pressure output of a FLAUT array is maximised by arranging the cell spacing to be as close as practically possible. Thus, the cells were spaced at multiples of 2.25 to the cavity radius - to reduce the risk of cell damage. An analytical method to simulate, and a technique to measure the inherent noise using a specially designed hybrid isolation vessel has been developed. From the measurement, the FLAUT noise is found to be 5.8 W, an improvement of 2.7 dB compared to the conventional cavity only design.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2013

Author dc:creator

• Hamid, Syamsul Bahrin Abdul

DOI

10.48730/br7j-hp55

Identifier

T13839

OAI identifier oai:identifier

oai:strathclyde:mg74qm10f