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Author = Lawlor, Bob;
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Displaying Results 1 - 25 of 47 on page 1 of 2
Marked
Mark
A comparison of time-domain time-scale modification algorithms
(2006)
Dorran, David; Lawlor, Bob; Coyle, Eugene
A comparison of time-domain time-scale modification algorithms
(2006)
Dorran, David; Lawlor, Bob; Coyle, Eugene
Abstract:
Time-domain approaches to time-scale modification are popular due to their ability to produce high quality results at a relatively low computational cost. Within the category of time-domain implementations quite a number of alternatives exist, each with their own computational requirements and associated output quality. This paper provides a computational and objective output quality assessment of a number of popular time-domain time-scaling implementations; thus providing a means for developers to identify a suitable algorithm for their application of interest. In addition, the issues that should be considered in developing time-domain algorithms are outlined, purely in the context of a waveform editing procedure.
http://mural.maynoothuniversity.ie/9712/
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Mark
A Hybrid Time-Frequency Domain approach to Audio time-scale modification.
(2006)
Dorran, David; Lawlor, Bob; Coyle, Eugene
A Hybrid Time-Frequency Domain approach to Audio time-scale modification.
(2006)
Dorran, David; Lawlor, Bob; Coyle, Eugene
Abstract:
Frequency-domain approaches to audio time-scale modification introduce a reverberant/phasy artefact into the time-scaled output. Such artefacts are generally not present within time-domain implementations; however, high quality time-scaling in the time domain is typically limited to quasi-periodic signals such as speech. A hybrid method of time-scaling is presented which draws upon appealing aspects of both time-domain and frequency domain implementations. The technique described can be successfully applied to a wide range of audio and is both robust and efficient. Subjective testing demonstrates that the technique significantly reduces the presence of phasiness.
http://mural.maynoothuniversity.ie/12736/
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A novel approach to Acoustic Echo cancellation
(2008)
Cahill, Niall M.; Lawlor, Bob
A novel approach to Acoustic Echo cancellation
(2008)
Cahill, Niall M.; Lawlor, Bob
Abstract:
In this paper a novel approach to single microphone Acoustic Echo cancellation (AEC) is presented. This approach performs AEC by employing techniques developed for monaural sound source separation. It is shown that the AEC problem can be cast in a monaural sound source separation framework and through this framework significant echo suppression can be achieved. The new approach is evaluated through experiments on simulated data.
http://mural.maynoothuniversity.ie/8806/
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A novel approach to mixed phase room impulse response inversion for speech dereverberation
(2008)
Cahill, Niall M.; Lawlor, Bob
A novel approach to mixed phase room impulse response inversion for speech dereverberation
(2008)
Cahill, Niall M.; Lawlor, Bob
Abstract:
Outlined in this paper is a novel approach to speech dereverberation when an estimate of the source-receiver transfer function is known. It is a two-stage algorithm based on the minimum phase/allpass decomposition of a mixed phase room impulse response (RIR). The reverberant speech is first filtered with the inverse minimum phase component of the RIR. Then a Non-Negative Matrix Factorization (NMF) based denoising approach is used to remove artifacts associated with the allpass component of the RIR from the inverse filtered speech. This approach was tested on speech convolved with synthetically generated room impulse responses. The results of these tests were analyzed using objective measures and listening tests both of which indicate that this approach leads to significant enhancement of the reverberant speech.
http://mural.maynoothuniversity.ie/8804/
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A Novel Efficient Algorithm for Music Transposition
(1999)
Lawlor, Bob; Fagan, A.D.
A Novel Efficient Algorithm for Music Transposition
(1999)
Lawlor, Bob; Fagan, A.D.
Abstract:
We present a novel efficient algorithm for scaling the frequency content of an audio signal by any desired factor in the range 0.5 (minus one octave) to 2.0 (plus one octave) enabling a recording to be played in any desired key without affecting the tempo. The algorithm uses an adaptive overlap-add (AOLA) technique to realise the desired frequency scaling without affecting the duration. Informal listening tests show output quality equal to that of a conventional overlap-add algorithm used in many commercially available systems, but offering significant computational saving relative to that algorithm. The algorithm is also used to simultaneously scale both the tempo and key of a recording.
http://mural.maynoothuniversity.ie/9709/
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A Novel Efficient Algorithm for Voice Gender Conversion
(1999)
Lawlor, Bob
A Novel Efficient Algorithm for Voice Gender Conversion
(1999)
Lawlor, Bob
Abstract:
Realistic Voice Gender Conversion (VGC) requires independent scaling of the glottal (pitch) and vocal tract (formant) related features of the input speech signal. We present a VGC algorithm which has two novel features. Firstly, an efficient frequency scaling algorithm is presented. Secondly, we use this to scale all frequencies in the input signal by the desired formant scaling factor. We then deconvolve the glottal contribution using a standard linear predictive analysis and frequency scale it further such that the desired pitch scaling factor is equal to the product of the two frequency scaling factors. Finally, we resynthesize the converted speech. The female-to-male results were excellent while the male-to-female results sounded synthetic.
http://mural.maynoothuniversity.ie/9766/
Marked
Mark
A novel high quality efficient algorithm for time-scale modification of speech
(1999)
Lawlor, Bob; Fagan, A.D.
A novel high quality efficient algorithm for time-scale modification of speech
(1999)
Lawlor, Bob; Fagan, A.D.
Abstract:
We present a novel efficient algorithm for time-scale modification (TSM) of speech which gives output quality equal to that of a conventional TSM algorithm, but having computational load an order of magnitude less. The algorithm presented uses a fixed length rectangular stepping window and a simple peak alignment criterion to track the local natural scaling factor and adapt the window step size. The desired TSM factor is realised by the appropriate number of applications of the constantly varying local natural scaling factor. The local natural scaling factor estimate is updated at sub-pitch period intervals giving accurate pitch tracking and high quality in the output scaled signal.
http://mural.maynoothuniversity.ie/9768/
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A resource management tool for implementing strategic direction in an academic department
(2005)
Ringwood, John; Devitt, Frank; Doherty, Sean; Farrell, Ronan; Lawlor, Bob; McLoone, Sea...
A resource management tool for implementing strategic direction in an academic department
(2005)
Ringwood, John; Devitt, Frank; Doherty, Sean; Farrell, Ronan; Lawlor, Bob; McLoone, Sean F.; McLoone, Seamus; Rogers, Alan; Villing, Rudi; Ward, Tomas E.
Abstract:
This paper reports on a load balancing system for an academic department, which can be used as an implementation mechanism for strategic planning. In essence, it consists of weighting each activity within the department and performing workload allocation based on this transparent scheme. The experience to date has been very positive, in terms of achieving strategic change and staff contentment.
http://mural.maynoothuniversity.ie/1287/
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A Transatlantic Conversation About Critical Thinking and Writing in STEM
(2014)
Farrell, Alison; Lawlor, Bob; Brabazon, Dermot; Casey, Kevin; Jordan, Anne; Strawbridge...
A Transatlantic Conversation About Critical Thinking and Writing in STEM
(2014)
Farrell, Alison; Lawlor, Bob; Brabazon, Dermot; Casey, Kevin; Jordan, Anne; Strawbridge, Judith
Abstract:
Abstract included in text.
http://mural.maynoothuniversity.ie/10184/
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An approach to doubletalk detection based on non-negative matrix factorization
(2008)
Cahill, Niall M.; Lawlor, Bob
An approach to doubletalk detection based on non-negative matrix factorization
(2008)
Cahill, Niall M.; Lawlor, Bob
Abstract:
In this paper a novel approach to doubletalk detection (DTD) is presented. This approach uses a modified Non-Negative Matrix Factorization (NMF) technique originally developed for monaural sound source separation to perform DTD. The efficacy of this approach is demonstrated through experiments using real room impulse responses (RIRs). The properties of this algorithm are then discussed with reference to experimental results.
http://mural.maynoothuniversity.ie/8803/
Marked
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An Efficient Phasiness Reduction Technique for Moderate Audio Time-scale Modification
(2004)
Dorran, David; Coyle, Eugene; Lawlor, Bob
An Efficient Phasiness Reduction Technique for Moderate Audio Time-scale Modification
(2004)
Dorran, David; Coyle, Eugene; Lawlor, Bob
Abstract:
Phase vocoder approaches to timescale modification of audio introduce a reverberant/phasy artifact into the time-scaled output due to a loss in phase coherence between short-time Fourier transform (STFT) bins. Recent improvements to the phase vocoder have reduced the presence of this artifact, however, it remains a problem. A method of time-scaling is presented that results in a further reduction in phasiness, for moderate timescale factors, by taking advantage of some flexibility that exists in the choice of phase required so as to maintain horizontal phase coherence between related STFT bins. Furthermore, the approach leads to a reduction in computational load within the range of time-scaling factors for which phasi-ness is reduced.
http://mural.maynoothuniversity.ie/8831/
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An Introduction to Enquiry/ Problem-based Learning, Maynooth: Facilitate and the All Ireland Society for Higher Education (AISHE)
(2015)
Delaney, Yvonne; Farrell, Alison; Hack, Catherine; Lawlor, Bob; McLoone, Seamus; Meehan...
An Introduction to Enquiry/ Problem-based Learning, Maynooth: Facilitate and the All Ireland Society for Higher Education (AISHE)
(2015)
Delaney, Yvonne; Farrell, Alison; Hack, Catherine; Lawlor, Bob; McLoone, Seamus; Meehan, Andrew; Philips, Declan; Richardson, Ita
Abstract:
The booklet is organized into two sections. Part 1 provides an overview which answers the broad question of what is enquiry/problembased learning. Part 2 presents four case studies of enquiry/problem-based learning. The booklet draws on a few key texts but particularly on another publication by Barrett and Cashman (eds) entitled A Practitioner’s Guide to Enquiry and Problem-based Learning (2010
http://mural.maynoothuniversity.ie/6824/
Marked
Mark
Application of Real-time AMDF Pitch Detection in a Voice Gender Normalisation System
(2002)
Jung, E.; Schwarzbacher, A.; Humphreys, K.; Lawlor, Bob
Application of Real-time AMDF Pitch Detection in a Voice Gender Normalisation System
(2002)
Jung, E.; Schwarzbacher, A.; Humphreys, K.; Lawlor, Bob
Abstract:
Traditionally the interest in voice gender conversion was of a more theoretical nature rather than founded in real-life applications. However, with the increase in mobile communication and the resulting limitation in transmission bandwidth new approaches to minimising data rates have to be developed. Here voice gender normalisation (VGN) presents an efficient method of achieving higher compression rates by using the VGN algorithm to remove gender specific components of a speech signal and thus enhancing the information content to be transmitted. A second application for VGN is in the field of speech controlled systems, where current speech recognition algorithms have to deal with the voice characteristics of a speaker as well as the information content. Here again the use of VGN can remove the speaker's voice gender characteristics and thus enhance the message contents. Therefore, such a system would be capable of achieving higher recognition rates while being independent of th...
http://mural.maynoothuniversity.ie/8825/
Marked
Mark
Audio Time-Scale Modification Using a Hybrid Time-Frequency Domain Approach
(2005)
Dorran, David; Coyle, Eugene; Lawlor, Bob
Audio Time-Scale Modification Using a Hybrid Time-Frequency Domain Approach
(2005)
Dorran, David; Coyle, Eugene; Lawlor, Bob
Abstract:
Frequency-domain approaches to audio time-scale modification introduce a reverberant artifact into the time-scaled output due to a loss in phase coherence between subband components. WHilst techniques have been developed which reduce the presence of this artifact, it remains a source of difficulty. A method of time-scaling is presented that reduces the presence of reverberation by taking advantage of some flexibility that exists in the choice of phase required so as to maintain horizontal phase coherence along frequency-domain subband components. The approach makes use of appearling aspects of existing time-domain and requency-domain time-scaling techniques.
http://mural.maynoothuniversity.ie/652/
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Mark
Comparison of Signal Reconstruction Methods for the Azimuth Discrimination and Resynthesis Algorithm
(2005)
Barry, Dan; Lawlor, Bob; Coyle, Eugene
Comparison of Signal Reconstruction Methods for the Azimuth Discrimination and Resynthesis Algorithm
(2005)
Barry, Dan; Lawlor, Bob; Coyle, Eugene
Abstract:
The Azimuth Discrimination and Resynthesis algorithm, (ADRess), has been shown to produce high quality sound source separation results for intensity panned stereo recordings. There are however, artifacts such as phasiness which become apparent in the separated signals under certain conditions. This is largely due to the fact that only the magnitude spectra for the separated sources are estimated. Each source is then resynthesised using the phase information obtained from the original mixture. This paper describes the nature and origin of the associated artifacts and proposes alternative techniques for resynthesising the separated signals. A comparison of each technique is then presented.
http://mural.maynoothuniversity.ie/9767/
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Demixing of Speech Mixtures and Enhancement of Noisy Speech Using ADRess Algorithm
(2006)
Cahill, Niall M.; Cooney, Rory; Humphreys, Kenneth; Lawlor, Bob
Demixing of Speech Mixtures and Enhancement of Noisy Speech Using ADRess Algorithm
(2006)
Cahill, Niall M.; Cooney, Rory; Humphreys, Kenneth; Lawlor, Bob
Abstract:
This paper describes the ability of the Azimuth Discrimination and Resynthesis algorithm (ADRess) to separate multiple speech signals from two mixtures in a simulation environment. ADRess exploits the spatial signature of each of the contributing speech sources to demix the mixtures. Speech sentences taken from the TIMIT database and noise signals from the NOISEX database were mixed synthetically to create pairs of mixtures. ADRess can exploit the spatial signature of noise and speech sources to remove or isolate them from a mixture. To simulate the spatial location of different sources the relative attenuation and phase difference of each source between the two mixtures were manipulated. This was performed for numerous different angles of arrival so as to robustly test the algorithm. Objective measures and promising informal listening test results show the suitability of ADRess for cleaning noisy speech mixtures and document the performance of ADRess for speech mixtures with differ...
http://mural.maynoothuniversity.ie/8813/
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Development of a crosstalk measurement type three-dimensional digital color decoder
(1993)
Ito, S.-E.; Lawlor, Bob; Ebihara, N.
Development of a crosstalk measurement type three-dimensional digital color decoder
(1993)
Ito, S.-E.; Lawlor, Bob; Ebihara, N.
Abstract:
A three-dimensional digital color decoder system that converts composite NTSC or PAL video signals into cross color-free high picture quality digital video signals is described. In this system, the Y/C crosstalk is measured by means of three-dimensional filters which the authors have devised to adaptively control the three-dimensional Y/C separation filters. The algorithm is realized as hardware, and the picture quality is improved by a rank of 1.5 at a slight distance of 4H over the conventional three-dimensional digital color decoders when various composite color video signals including still images, slowly moving images, and moving circular zone plates are input.
http://mural.maynoothuniversity.ie/9759/
Marked
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Drum Source Separation using Percussive Feature Detection and Spectral Modulation
(2005)
Barry, Dan; Fitzgerald, Derry; Coyle, Eugene; Lawlor, Bob
Drum Source Separation using Percussive Feature Detection and Spectral Modulation
(2005)
Barry, Dan; Fitzgerald, Derry; Coyle, Eugene; Lawlor, Bob
Abstract:
We present a method for the separation and resynthesis of drum sources from single channel polyphonic mixtures. The frequency domain technique involves identifying the presence of a drum using a novel percussive feature detection function, after which the short-time magnitude spectrum is estimated and scaled according to an estimated time-amplitude function derived from the percussive measure. In addition to producing high quality separation results, the method we describe is also a useful pre-process for drum transcription techniques such as Prior Subspace Analysis in the presence of pitched instruments.
http://mural.maynoothuniversity.ie/699/
Marked
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Drum Transcription using Automatic Grouping of Events and Prior Subspace Analysis
(2003)
Fitzgerald, Derry; Lawlor, Bob; Coyle, Eugene
Drum Transcription using Automatic Grouping of Events and Prior Subspace Analysis
(2003)
Fitzgerald, Derry; Lawlor, Bob; Coyle, Eugene
Abstract:
While Prior Subspace Analysis (PSA) has proved an effective tool for transcribing mixtures of snare, kick drum and hi-hat both in the "drum-only" case and in the presence of pitched instruments attempts to extend it to deal with increased numbers of drum types have met with mixed results.To overcome this an automatic modeling and grouping procedure has been developed which groups drum events on the similarity of their frequency content. Combining this procedure with PSA allows the extension of PSA to robustly handle greater numbers of drum types. The effectiveness of this approach is demonstrated in a drum transcription algorithm.
http://mural.maynoothuniversity.ie/734/
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GSE1 Postgraduate Information Literacy and Communication Skills Training-Project Orientated Delivery
(2013)
Downey, Liam; Lawlor, Bob; Quinn, Ciaran
GSE1 Postgraduate Information Literacy and Communication Skills Training-Project Orientated Delivery
(2013)
Downey, Liam; Lawlor, Bob; Quinn, Ciaran
Abstract:
Module presented by the Faculty of Science and Engineering in cooperation with the Subject Librarian from Learning Teaching and Research Development in the Library. Original format was four three hour workshops plus 18 hrs self paced course work using interdisciplinary written and verbal skills training tasks . Translate a peer reviewed Journal paper to communicate it to a interdisciplinary audience and prepare a short presentation. It was enhanced with the introduction of a peer-learning component by dividing participants into four groups of eight. A project orientated and problem based learning (POPBL) approach has been shown to work well in the delivery of educational outcomes and also in the delivery of Information Literacy
http://mural.maynoothuniversity.ie/4352/
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Harmonic Sound Source Separation using FIR Comb Filters
(2004)
Gainza, Mikel; Lawlor, Bob; Coyle, Eugene
Harmonic Sound Source Separation using FIR Comb Filters
(2004)
Gainza, Mikel; Lawlor, Bob; Coyle, Eugene
Abstract:
A technique for separating harmonic sound sources using FIR comb filters is presented. First, a pre-processing task is performed by a multipitch estimator to detect the pitches that the signal is composed of. Then, a method based on the Short Time Fourier Transform (STFT) is utilized to iteratively extract the harmonics belonging to a given source by using FIR comb filters. The presented approach improves upon existing sinusoidal model approaches in terms of the perceptual quality of the extracted signal.
http://mural.maynoothuniversity.ie/722/
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High quality time-scale modification of speech using a peak alignment overlap-add algorithm (PAOLA)
(2003)
Dorran, David; Lawlor, Bob; Coyle, Eugene
High quality time-scale modification of speech using a peak alignment overlap-add algorithm (PAOLA)
(2003)
Dorran, David; Lawlor, Bob; Coyle, Eugene
Abstract:
The duration of a speech passage can be altered using audio time-scale modification techniques. Time-scale modification can be achieved in the time domain by segmenting the input signal into overlapping frames and recombining the frames with an overlap differing from the analysis overlap. We present a time-scale modification algorithm that uses a simple peak alignment technique to synchronize overlapping synthesis frames. The peak alignment overlap-add (PAOLA) algorithm also takes advantage of waveform properties to ensure a high quality output for the minimum number of iterations. The new algorithm produces a time-scaled output of approximately equal quality to that of an adaptive implementation of the commercially popular synchronised overlap-add (SOLA) algorithm, but offers a computational saving ranging from a factor of 15 (for a time-scale factor of 0.5) to 170 (for a time-scale factor of 1.1).
http://mural.maynoothuniversity.ie/8791/
Marked
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Implementation of real-time AMDF pitch-detection for voice gender normalisation
(2002)
Jung, E.; Schwarzbacher, A.; Lawlor, Bob
Implementation of real-time AMDF pitch-detection for voice gender normalisation
(2002)
Jung, E.; Schwarzbacher, A.; Lawlor, Bob
Abstract:
Traditionally the interest in voice gender conversion was of a more theoretical nature rather than founded in real-life applications. However, with the increase in mobile communication and the resulting limitation in transmission bandwidth new approaches to minimising data rates have to be developed. Here voice gender normalisation (VGN) presents a novel method of achieving higher compression rates by using the VGN algorithm to remove all gender specific components of a speech signal and thus leaving only the information content to be transmitted. A second application for VGN is in the field of speech controlled systems, where current speech recognition algorithms have to deal with the voice characteristics of a speaker as well as the information content. Here again the use of VGN can remove the speakers voice characteristics leaving only the pure information. Therefore, such a system would be capable of achieving much higher recognition rates while being independent of the speaker....
http://mural.maynoothuniversity.ie/8788/
Marked
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Improved performance Speech codec for mobile communications
(2002)
Humphreys, K.; Lawlor, Bob
Improved performance Speech codec for mobile communications
(2002)
Humphreys, K.; Lawlor, Bob
Abstract:
This paper presents the application of a Voice Gender Normalization algorithm to the GSM Speech Codec and describes the refinements that can be made to the Codec as a result. By reducing the dynamic range of the speech signals entering the Codec gender specific adaptations can be made to the Codec to improve its performance in terms of subjective sound quality or its transmitted bit rate.
http://mural.maynoothuniversity.ie/9764/
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Independent Subspace Analysis using Locally Linear Embedding
(2003)
Fitzgerald, Derry; Lawlor, Bob; Coyle, Eugene
Independent Subspace Analysis using Locally Linear Embedding
(2003)
Fitzgerald, Derry; Lawlor, Bob; Coyle, Eugene
Abstract:
While Independent Subspace Analysis provides a means of blindly separating sound sources from a single channel signal, it does have a number of problems. In particular the amount of information required for separation of sources varies with the signal. This is as a result of the variance-based nature of Principal Component Analysis, which is used for dimensional reduction in the Independent Subspace Analysis algorithm. In an attempt to overcome this problem the use of a non-variance based dimensional reduction method, Locally Linear Embedding, is proposed. Locally Linear Embedding is a geometry based dimensional reduction technique. The use of this approach is demonstrated by its application to single channel source separation, and its merits discussed.
http://mural.maynoothuniversity.ie/694/
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