A selection of tutorials to help you in your research.
Introduction for hydrophone users on the basics of hydrophone sensitivity and frequency response. Sample response for some of the different types of hydrophone is presented. The relevance of hydrophone frequency response, in the context of the type of field being measured, is also discussed.
Introduction to hydrophone directivity and spatial averaging. The causes of both effects are discussed and the means by which directional response is determined experimentally are presented.
This tutorial provides an introduction to fibre-optic hydrophones and their methods of operation. It also discusses some features that set this class of hydrophones apart from conventional piezo-electric ones.
Introduction to the method to convert hydrophone output voltage to a pressure waveform. The general concept of deconvolution is presented as well as the narrowband approximation and when it may be used.
This short tutorial explains how hydrophone preamplifiers preserve signal integrity from both an impedance buffering, and immunity to electro-magnetic noise, point of view.
This tutorial provides an introduction to the construction, properties and usage of needle hydrophones. The variation in sensitivity, frequency response and directivity for a range of hydrophone sizes is also presented.
This tutorial provides an introduction to the construction, properties and usage of membrane hydrophones. The effect of membrane film thickness on hydrophone sensitivity and frequency response is presented. The Lamb wave artefact that influences the directivity of membrane hydrophone at low frequencies and oblique incidence is also discussed.
This tutorial looks at the triple challenges associated with attempting to record the acoustic signals generated by cavitating bubbles: the masking effect of high amplitude drive signals, the positional uncertainty of the source bubble arising from the stochastic nature of cavitation and the potential for sensor damage. Mitigation strategies are presented alongside advice on how to align source transducers and PCDs in both con-focal and co-axial configurations.
Ultrasonic transducer tutorials
One of a 3-part mini-series on ultrasonic transducers, demonstrating how the choice of excitation signal can impact both the ultrasonic signal generated by the transducers and the ease of making subsequent measurements.
One of a 3-part mini-series on ultrasonic transducers. This tutorial video extends upon the previous discussion of excitation signals and illustrates how radiated field patterns due to the interaction of edge and plate wave contributions.
Instrumentation and measurement tutorials
Presentation given at the Acoustical Society of America’s “Acoustics Virtually Everywhere” conference in December 2020. This paper discusses the challenges associated with making hydrophone measurements in nonlinear fields
This tutorial attempts to address some of the confusion about ultrasonic intensity. It provides clear illustrations of how variations in averaging (be that spatial or temporal) can affect the resulting calculated values, and as a consequence why Output Beam intensity and focal Intensity can differ by orders of magnitude.
Fundamental science tutorials
Topics covered are: how sinusoids combine to represent time domain waveforms, why do we use window functions, what are convolutions, and how is it useful with real-world systems. Contains a number of animations to help illustrate important concepts.
The tutorial provides an introduction to transmission lines and the manner that they can be implemented with ABCD Matrices. Transmission lines are an important concept in the simulation of both ultrasonic and electronic devices and examples of both are included within this tutorial.
This tutorial presents the viewer with an overview of nonlinear ultrasonic propagation. Waveform distortion and the corresponding harmonic generation are presented along with a number of waveforms to assist in the identification of nonlinear propagation effects.
This tutorial discusses the complex-valued nature of impedance and how both real and ideal components behave in response to AC. It also discusses how we can use frequency-dependent impedance to form low, high, band-pass and band-stop filters.
This tutorial describes the physics of reflection and transmission phenomena and how this relates to forming an ultrasound image. Greyscale transformations are discussed alongside A-, B- and C-scale images. The principles of ultrasonic thickness gauging and defect detection are also presented.
There are many similarities between the mathematical descriptions of acoustic and electrical behaviour. This tutorial identifies the key variables, components that may be used in equivalent circuits and the equations that describe the relationships.
This tutorial introduces the different types of ultrasonic signatures that can be expected from non-inertial and inertial cavitation events. Examples of experimental cavitation signatures, containing a wide variety of spectral components, are provided.
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