PhD in Acoustic Engineering

Clever engineering is required in all vehicles nowadays to achieve passenger comfort whilst also minimising vehicle weight. Cars, buses, trains and ships all require diagnostic testing to help reduce noise and vibration generated by rolling on the road or track and mechanical components, engines, pumps etc.. Similar techniques are also needed in aircraft. In this PhD, new techniques will be developed for analysing multi-channel acoustic and vibration signals from vehicles in operation. This will improve analysis of how noise and vibration is generated and transmitted through the vehicle and lead to quieter vehicles and /or weight reductions. Candidates will need a good degree or Masters in Mechanical Engineering. Contact a.t.moorhouse@salford.ac.uk

Railways will become increasingly important as fuel gets more expensive. This PhD project will look at predicting and minimising the effect of vibration on people living and working near to rail tracks. The project will build on research carried out under the European seventh framework and by the UK government. The research can be oriented towards the generation and propagation of vibration through the ground and into buildings, or candidates with a background in Environmental Engineering may wish to emphasise the effect of vibration on human activities. Contact d.c.waddington@salford.ac.uk

Metamaterials possess useful properties not found in naturally-occurring or other manmade materials. In metamaterials, the effective density and elastic moduli can attain negative values. When one of these quantities is negative, the medium does not support any propagating waves in a range of frequencies and there is a “stop band". This provides an opportunity of using them as nearly perfect compact noise screens. Few of the potential metamaterial noise control applications have been investigated so far. The proposed research will respond to the engineering challenge of finding lightweight materials for sound and vibration reduction particularly at low frequencies. The project will contribute particularly to the reduction of noise and vibration at frequencies below 250Hz since such low frequencies are attenuated less by walls and other structures in common constructions and can cause severe disturbance. As well as having many civilian applications, this is of military interest as metamaterials could be used as effective blast reflectors. Contact o.umnova@salford.ac.uk

Rain noise is an important consideration nowadays in the design of schools, sports halls and many other buildings. A standard measurement method was introduced in 2006 (ISO 140:18 - based largely on research carried out at Salford during the early 1990s) which allows roof constructions to be characterised and rated in terms of their rain noise performance. The current rain noise research aims to extend earlier work so as to develop faster and more adaptable measurement methods as well as prediction models. It will also extend the ‘Rain Noise Simulator’, developed during various student projects; the simulator produces realistic simulated sounds of any type of rainfall falling on a roof tested in ‘dry’ conditions, i.e. without any real or artificial rainfall.Contact a.t.moorhouse@salford.ac.uk

Conventional porous absorbers have poor low frequency performance unless very thick layers are used. This project focuses on the development of new porous absorbers which can overcome this limitation. Low frequency absorption can be improved by introducing two very different scales of the pores, however so far only very simplistic geometries have been studied. We would like to investigate whether the introduction of multiple scales (i.e. pores with more than two characteristic sizes) can dramatically improve performance. While materials with multiple pore scales are well known (e.g. vermiculite), their acoustical applications are currently limited. A general theoretical approach to modelling multi-scale porous structures needs to be developed. It will then be possible to identify and optimise those material parameters which are most important for the acoustical performance. Contact o.umnova@salford.ac.uk

Salford have a track record in developing hearing protective devices (HPDs), in electro acoustic transducer design, and in signal processing for active noise control. This PhD program aims to combine these areas of expertise, in developing new techniques and devices for challenging noise environments. Contact m.r.avis@salford.ac.uk

A Virtual Acoustic Prototype (VAP) is a way of listening to a not-yet-existing machine in operation. It involves measurements and/or modelling of machine components which are then combined in the computer to produce a realistic sound of the full working machine. VAPs have been generated at Salford for various domestic products including washing machines and fan units, lawnmowers and automotive steering systems. Correct treatment of structure-borne sound is the speciality of the Salford team, headed by Prof. Andy Moorhouse. The methodology is general and can be applied to more or less any type of machine to predict the product sound, and even to rain noise on metal roofs. There is broad scope for research to develop VAPs of many more types of machines and products. Contact a.t.moorhouse@salford.ac.uk

Numerical methods are an important part of many engineering design packages for a wide variety of engineering disciplines and the ability to use them to simulate possible designs is a vital part of modern design. Many of them such as finite element methods, and others, are computationally intensive and this has limited their full application to larger problems. Recently graphics processor units (GPUs), which can be found as standard in modern computers, have been used to provide a large computation engine for such problems. However, a simple transfer of existing algorithms does not provide the best route for implementation. The GPU has a reverse time cost between computation and memory access in that computation is very quick but memory access is up to 200 times slower. Most traditional algorithms have been developed with the paradigm that memory access is quick but computation is slow. Thus algorithms that required expensive computation for lower memory access requirements were ignored. These now may be more suitable for GPU implementation. The purpose of this project is to examine ways of using more computationally intensive kernels that reduce the number of memory access needed for the full simulation. As computation methods are applicable over a broad range of engineering problems the specific application domain can be adjusted to fit the background needs of the student or sponsor.

There is a need to produce metadata from TV and radio programme content using automatic techniques. Currently, there is great interest in semantic metadata for indexing and searching, for instance the BBC is looking to automatically analyse audio and video content, extracting key semantic themes and ideas to allow programme classification and clustering. For your PhD you would look at analysing music within programmes to ascertain what semantic or emotive information (e.g. happy, sad, exciting, calm) can be extracted via Music Information Retrieval (MIR) techniques. Music is well documented as setting or heightening semantic intent within broadcast programmes. By extracting these semantics much richer metadata would be created, allowing for better classification and searching for viewers. For audio processing, initially music needs to be identified within the programme and separated from competing sounds. Then the music’s key features will be extracted e.g. tempo, tonality. The audio features will give basic information about the content of the programme music. They will to be used to identify the music’s semantic concepts using an experiential based learning algorithm, such as a support vector machine. This will enable an automated semantic metadata extraction system for music. Although computer scientists have studied automatic extraction of semantics from audio before, the use of knowledge from music is surprisingly lacking from much of the work, and this gives great potential for the proposed collaboration between an acoustic engineer and a music composer to break new ground. Furthermore, music within TV and radio has largely been ignored by academia and consequently new research and publications in musicology can be achieved. Contact t.j.cox@salford.ac.uk

Despite the advance of visualisation and auralisation research over the last few decades, the fusing together of the two technologies is still unsatisfactory. What often happens is a world-class facility in one area (e.g. vision) has less than excellent facilities in the other (e.g. sound). This places severe limits on the realism VR simulations, the virtual environments they create, especially how immersive it is. At Salford we have been working to integrate auralization and visual simulations together for the last few years. We are about to complete a near million pounds upgrade on both our acoustic and visualization research facilities to create a infra-structure that would allow multi-modal virtual reality simulation with both world-class acoustics and visualisation. This PhD research project will use these upgraded facilities to address interfacing questions, as well as the impact of using different complexity of configurations on realism. The aim of the doctoral research would be to develop different integration strategies that can suit differing requirements of applications such as teleconferencing, virtual studios, and virtual workspaces. Contact y.w.lam@salford.ac.uk

Some CDs sound great and some don’t: the sound quality of audio programme material is very variable. Expert and naïve listeners are quite good at picking up these differences in sound quality. However, so far there are no metrics that can quantify if a given music track is of good quality or not. This PhD project aims to define and extract quality features from audio signals that enable an automated rating of the acoustic quality therein. The technical aspects of the research project will be underpinned by a substantial study of human factors that determine perceived quality in sound and audio production. The foreseen outcomes are: 1) A framework that sets the relative importance of various objective acoustic measures of signal content in the context of human listening; 2) A digital tool that automatically rates and improves audio quality in a given stream. Applications of the knowledge and technology span from automated adjustment to different reproduction scenarios (eg: radio speech in a car vs. live sound) to archive recovery. Contact B.M.Fazenda@salford.ac.uk

At the mixing stage in Audio Production, the professional option is to use expensive, specialist facilities. However, an increasing amount of sound production work gets done ‘on the move’ using laptops or working in offices. There is a need for better sound monitoring through headphones. Currently, headphone monitoring has its own inherent problems both in stereo and multichannel (e.g. 5.1) program presentation.

This PhD acoustics project proposes to develop a critical monitoring system for headphone reproduction. Research will investigate advanced digital signal processing techniques alongside a study of human listening factors to produce a system that enables sound engineering work outside a controlled studio environment. The outcomes of the doctoral project will result in hardware or software application crucial to the current trends of the sound production industry. Contact B.M.Fazenda@salford.ac.uk

The monitoring of noisy machines or other facilities is crucial for maintenance and optimal performance. The use of acoustic emission signals, the sound made by the devices, is a promising technique but background noise and acoustic effects caused by enclosures cause problems. This PhD project aims to develop acoustic arrays and signal analysis techniques that enhance the detection of a quiet signal amidst loud sounds generated by other close-proximity noise sources. The application of such technology is important in detecting faults in large engines or factory floors with a large number of machines. The application of intelligent systems, such as artificial neural networks (ANN) and independent component analysis (ICA), will be employed in the doctoral research to develop microphone arrays that effectively increase the gain for a particular direction allowing the detection of independent acoustic sources. Contact B.M.Fazenda@salford.ac.uk

Reliable and fast methods of measuring sound insulation are vitally important for ensuring the quality of new buildings. However, the current measurement standards do not work well at low frequencies where most complaints occur. This doctoral research project will investigate novel measurement methods adapted for low frequencies that will complement existing standard methods. The research programwill involve both theoretical and practical work and will draw on work carried out in numerous student projects. It will exploit the state-of-the-art laboratories at Salford and our 40 plus years of experience as an accredited laboratory for sound insulation measurement. Contact a.t.moorhouse@salford.ac.uk

Diffusers are used to disperse sounds. In small rooms, such as studios, they smear early arriving reflections which otherwise could cause distortion. In larger spaces, such as auditoria, concert halls and theatres, they might be used to form stage or audience canopies to evenly distribute sound around the space. In the last few decades, many new types of diffusers have been developed, but still crucial aspects need researching. For instance, subjective testing is needed to evaluate the true perceptual worth of diffusers - such a phd could expand to develop binaural coloration measures which currently don't work well. Other doctorates could explore prediction and measurement methods for diffusers, for instance the former might research time domain methods while the latter might explore in-situ measurement techniques. Contact t.j.cox@salford.ac.uk

Acoustic studies of ancient monuments is relatively scarce before the Greek and Roman eras when amphitheatres were central to these societies. Studies into the behaviour of sound in Neolithic archaeological sites show recurring and interesting acoustic effects, which would have been audible to our ancestors. Understanding the acoustics helps archaeologists and historians understand what the people using or constructing these places would have intended. This project intends to develop a methodology for a new area in archaeology and acoustics. The project involves the study of ancient sites around the world and includes measurements and modelling with room acoustic software, finite element analysis and wave based acoustic models. Contact B.M.Fazenda@salford.ac.uk

Good acoustics in classrooms is needed to enable pupils and teachers to communicate. Poor acoustics has been shown to affect learning and attainment. Research work has naturally concentrated on classrooms, but what about other areas of the school such as gymnasiums, canteens and corridors. Does the acoustic affect the behaviour of pupils and the ability of teachers to manage that behaviour? What are appropriate design guidelines for such spaces? Contact t.j.cox@salford.ac.uk

Advances in technology (Bluetooth headsets, ‘iPods’, quieter cars, helmets) are leading to situations where an individual's perception of the surrounding environment is hindered, making him/her more vulnerable to accidents and/or intentional dangers. Examples include: a driver unaware of a fast moving emergency vehicle; a motorbike or cyclist wearing a protection helmet; a civil protection foraging robot or vehicle on patrol. This PhD research project aims to study and develop detection and warning systems for users or equipment, allowing constant sound monitoring of the environment and identification of potential threats. The project straddles across a set of multi-disciplinary skills such as sensor engineering (with particular emphasis on acoustic detection), digital signal processing and cognitive behaviour. The research and development of advanced acoustic sensor networks and associated signal acquisition and analysis would form the core of the doctorate. Collaboration with psychology and social sciences partners will be provided to support the areas of cognition and human behaviour. Contact B.M.Fazenda@salford.ac.uk

Finger nails scrapping down a blackboard, the scream of a baby, your neighbour’s dog barking, someone throwing up: what is the worst sound in the world? In 2005/6 I ran a large scale web experiment to examine the worst sound in the world which attracted millions of votes. While the website has produced interesting results on people’s responses to the sounds, it is still unclear how valid the results are? In this phd research project, you will carry out perceptual measurements in the laboratory to compare to web experiment results, to determine the limitations of testing subjective responses over the Internet. Can the vast number of respondents available via the Internet compensate for the very uncontrolled experimental conditions? Contact t.j.cox@salford.ac.uk

Surround sound systems are becoming more commonplace for applications such as entertainment, auralisation, teleconferencing and military purposes. But how should the quality of spatial reproduction be measured? Perceived quality in spatial audio can be measured using both objective and subjective techniques. This project will investigate the adaptation of acoustical measures of spaciousness to reproduced sound and develop subjective testing techniques to compliment the objective measurements. The findings of the project will be used to evaluate the perceptually tolerable limits of compromise in spatial audio systems. In particular, the effects of non-standard loudspeaker set-ups, non-ideal listening environments and audio data compression techniques will be evaluated. Contact Jos Hirst

Understanding and utilising to best effect multiple sensory cues within virtual reality environments has been a focus of much ongoing research. Of particular interest to the us is the assessment of mediated aural cues within a wider multi-sensoral context. Such work is being facilitated by Salford University’s two in-house developed 256 wavefield synthesis systems and their associated API. The faithful rendering of virtual acoustic environments is comprised by the limitations of acoustic and visual mediating systems and their host environment. However, there is much scope for investigating and hence optimising pathological cue rejection and desired cue consolidation. Contact Ian Drumm

5. Affective response to amplitude modulated wind turbine sound

Recent research has shown that soundscapes are important in defining the character of a place or scene and in influencing the perceived quality. Unfortunately, soundscape has not always been a fully integral part of modern urban city planning, where visual aesthetics and material sustainability dominate. Usually only a noise pollution, is considered, which is a small and extreme part of the soundscape. This project will attempt to change this by looking at the impact of soundscape in urban regeneration scenarios. Virtual audio and visual rendering will be used together to create virtual reality (VR) simulations. Human responses to these will then be tested to determine if a significant change of attitude can be effected by changing the soundscape. Contact y.w.lam@salford.ac.uk

Growing concerns about climate change have led to an increased interest and investment in the development and deployment of low carbon technologies.
Wind farms are now ubiquitous as a sustainable method for harvesting wind energy. Due to the availability of adequate area and levels of nuisance to human environment, these are commonly deployed in remote sites and off-shore locations where monitoring and maintenance of units is typically costly. Remote acoustic monitoring presents advantages that could provide an efficient solutions. An independent and remote system, i.e not mounted on the turbine, is able to monitor various elements of a turbine and detect various types of fault from the sound emitted by the turbines. This PhD project aims to research methods to extract a wind turbine’s acoustic signature and, by advanced analysis, determine the condition of its various components. Signal detection and analysis techniques will be a starting point, although more advanced techniques such as blind source separation and machine learning methods will also be part of the doctoral research. Contact B.M.Fazenda@salford.ac.uk