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Precision Acoustics

Video Tutorials

A selection of tutorials to help you in your research.

Hydrophone tutorials

Hydrophone sensitivity and frequency response

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.

Hydrophone directivity and spatial averaging

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.

An introduction to fibre-optic hydrophones

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.

Converting hydrophone output voltage to pressure

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.

Hydrophone preamplifiers and signal integrity

This short tutorial explains how hydrophone preamplifiers preserve signal integrity from both an impedance buffering, and immunity to electro-magnetic noise, point of view.

Needle hydrophones

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.

Membrane hydrophones

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.

Passive cavitation detectors

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.

Choosing a hydrophone

This video tutorial considers all the different factors that affect selection of a hydrophone. Multiple factors are considered: sensitivity, directivity, frequency response, spatial averaging, environment and source signal duration.

Whilst its not possible to provide a rigorous method to select a hydrophone, this tutorial proposes a route to ensure all relevant factors are considered. The inherent nature of finding an optimal compromise between potentially mutually contradictory requirements is presented. There is also a brief discussion that highlights why some hydrophone types are more suitable for specific applications than others.

Ultrasonic transducer tutorials

Construction, bandwidth and damping

One of a 3-part mini-series on ultrasonic transducers, discussing the basics of transducer construction and how this can impact damping and thus bandwidth.

Choosing an excitation signal

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.

Radiated field patterns

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

Oscilloscope impedance and ultrasonic measurements

An introduction for hydrophone users on the importance of selecting the correct oscilloscope impedance when making ultrasonic measurements.

Oscilloscope setup for hydrophone measurement

A brief tutorial on the fundamentals of oscilloscope setup when conducting hydrophone measurements.

Uncertainty in ultrasonic measurement

A very brief introduction to the topic of measurement uncertainty and how it applies in ultrasonic measurements.

Ultrasonic power measurement

An overview of ultrasonic power measurement including the use and limitations of both radiation force balances, and scanned hydrophone measurements.

Addressing the challenges of hydrophone measurements in nonlinear ultrasonic fields

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

Ultrasonic intensity

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

Introduction to Fourier Transforms and their application

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.

Transmission lines and ABCD matrices

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.

Ultrasonic nonlinear propagation

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.

Electrical impedance and AC

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.

Forming images with ultrasound

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.

Acoustical and electrical analogies

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.

Cavitation signatures

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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