Rebecca Vos - Academia.edu (original) (raw)

Papers by Rebecca Vos

Speech Communication, Apr 1, 2023

Journal of Voice, 2018

0.1. Introduction At the upper end of the soprano singing range, singers alter the shape of their... more 0.1. Introduction At the upper end of the soprano singing range, singers alter the shape of their vocal tract to bring one or more of the vocal tract resonances nearer to a harmonic of the voice source. This is a process known as resonance tuning, which increases the amplitude of the sound produced with little effort from the singer. This study investigates the perception of first and second resonance tuning, key strategies observed in classically trained soprano voices. It was expected that the most commonly-used strategies observed in singers would be preferred by listeners as part of a subjective test. This test also allows for comparison of different tuning strategies between vowels, whereas previous investigations have usually focussed only on a single vowel sound (usually /A/). 0.2. Method Synthetic vowel sounds are generated using the Liljencrants-Fant glottal flow model, passed through a series of filters to represent the vocal tract resonances. Listeners then compared the sounds, which included 3 vowels, at 4 fundamental frequencies (f 0), to which 4 different tuning strategies are applied: (A) the expected formant values in speech, (B) the first formant tuned to the fundamental, (C) the second formant tuned to the second harmonic, and (D) both first and second formants tuned to the first and second harmonics respectively. Participants were asked three sets of questions: comparing how much they preferred different tuning strategies, how natural they found different tuning strategies, and identifying the vowel for each sound.

0.1. Introduction Soprano singers face a number of specific challenges when singing vowels at hig... more 0.1. Introduction Soprano singers face a number of specific challenges when singing vowels at high frequencies, due to the wide spacing of harmonics in the voice source. The varied and complex techniques used to overcome these are still not fully understood. Magnetic resonance imaging (MRI) has become increasingly popular in recent years for singing voice analysis. This study proposes a new protocol using 3D MRI to investigate the articulatory parameters relevant to resonance tuning, a technique whereby the singer alters their vocal tract to shift its resonances nearer to a voice source harmonic, increasing the amplitude of the sound produced. 0.2. Method The protocol was tested with a single soprano opera singer. Drawing on previous MRI studies, articulatory measurements from 3D MRI images were compared to vocal tract resonances measured directly using broad-band noise excitation. The suitability of the protocol was assessed using statistical analysis. 0.3. Results No clear linear relationships were apparent between articulatory characteristics and vocal tract resonances. The results were highly vowel-dependent, showing different patterns of resonance tuning and interactions between variables. This potentially indicates a complex interaction between the vocal tract and sung vowels in soprano voices, meriting further investigation. 0.4. Conclusion The effective interpretation of MRI data is essential for a deeper understanding of soprano voice production, and in particular the phenomenon of resonance tuning. This paper presents a new protocol that contributes towards this aim, and the results suggest that a more vowel-specific approach is necessary in the wider investigation of resonance tuning in female voices.

Soprano singers are capable of singing at pitches exceeding 1000 Hz, where the spacing of the har... more Soprano singers are capable of singing at pitches exceeding 1000 Hz, where the spacing of the harmonics means that the vocal tract resonances are not fully utilised. Sopranos therefore move the articulators, to "tune" the resonances of the vocal tract near to harmonics of the voice source, improving the efficiency of sound production. Although resonance tuning has been observed in soprano singers, it is not yet understood how this phenomenon is achieved and which articulators play the most significant roles in altering the vocal tract resonances. A preliminary experiment explored the use of broad band noise excitation of the vocal tract to observe resonance tuning behaviour in girl choristers. A second experiment extended this procedure to include MRI to observe the vocal tracts of 6 professional soprano opera singers and investigate how the articulators affect vocal tract resonances. The effects of MRI measurement conditions on singers were also investigated to establish whether measurements obtained during MRI are representative of normal singing. Finally, a perceptual test was conducted to study the perception of different methods of resonance tuning. As expected, considerable R 1 :f 0 tuning, and some R 2 :2f 0 tuning was observed in both groups. MRI revealed some links between resonances and articulators, however no consistent patterns in production were observed across subjects. The results showed strong differences in resonance production between different vowels and subjects, suggesting that resonance tuning production is not only a complex and context-specific topic, but also highly individual.

2022 International Workshop on Acoustic Signal Enhancement (IWAENC)

IEEE/ACM Transactions on Audio, Speech, and Language Processing

Acoustic beamforming is routinely used to improve the SNR of the received signal in applications ... more Acoustic beamforming is routinely used to improve the SNR of the received signal in applications such as hearing aids, robot audition, augmented reality, teleconferencing, source localisation and source tracking. The beamformer can be made adaptive by using an estimate of the time-varying noise covariance matrix in the spectral domain to determine an optimised beam pattern in each frequency bin that is specific to the acoustic environment and that can respond to temporal changes in it. However, robust estimation of the noise covariance matrix remains a challenging task especially in non-stationary acoustic environments. This paper presents a compact model of the signal covariance matrix that is defined by a small number of parameters whose values can be reliably estimated. The model leads to a robust estimate of the noise covariance matrix which can, in turn, be used to construct a beamformer. The performance of beamformers designed using this approach is evaluated for a spherical microphone array under a range of conditions using both simulated and measured room impulse responses. The proposed approach demonstrates consistent gains in intelligibility and perceptual quality metrics compared to the static and adaptive beamformers used as baselines.

ICASSP 2021 - 2021 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Multichannel acoustic signal processing is predicated on the fact that the interchannel relations... more Multichannel acoustic signal processing is predicated on the fact that the interchannel relationships between the received signals can be exploited to infer information about the acoustic scene. Recently there has been increasing interest in algorithms which are applicable in dynamic scenes, where the source(s) and/or microphone array may be moving. Simulating such scenes has particular challenges which are exacerbated when real-time, listener-in-the-loop evaluation of algorithms is required. This paper considers candidate pipelines for simulating the array response to a set of point/image sources in terms of their accuracy, scalability and continuity. A new approach, in which the filter kernels are obtained using principal component analysis from time-aligned impulse responses, is proposed. When the number of filter kernels is ≤ 40 the new approach achieves more accurate simulation than competing methods.

Applied Acoustics, 2022

Hypernasality is a disorder where excess nasal resonance is perceived during speech, often as a r... more Hypernasality is a disorder where excess nasal resonance is perceived during speech, often as a result of abnormal coupling between the oral and nasal tracts known as velopharyngeal insufficiency (VPI). The most common cause of VPI is a cleft palate, which affects around 1 in 1650 babies, around ⅓ of whom have persistent speech problems after surgery. Current equipment-based assessment methods are invasive and require expert knowledge, and perceptual assessment methods are limited by the availability of expert listeners and differing interpretations of assessment scales. Spectral analysis of hypernasality within the academic community has resulted in potentially useful spectral indicators, but these are highly variable, vowel specific, and not commonly used within clinical practice. Previous works by others have developed noise excitation technologies for the measurement of oral tract transfer functions using resonance measurement devices (RMD). These techniques provide an opportunity to investigate the structural system abnormalities which lead to hypernasality, without the need for invasive measurement equipment. Thus, the work presented in this study adapts these techniques for the detection of hypernasality. These adaptations include augmentation of the hardware and development of the software, so as to be suitable for transfer function measurement at the nostrils rather than the mouth (nRMD). The new method was tested with a single participant trained in hypernasal production, producing ‘normal’ and hypernasal vowels, and the recordings validated through a listening test by an expert listener and calculation of nasalance values using a nasality microphone. These validation stages indicated the reliability of the captured data, and analysis of the nRMD measurements indicated the presence of a systematic difference in the frequency range 2 to 2.5 kHz between normal and hypernasal speech. Further investigation is warranted to determine the generalisability of these findings across speakers, and to investigate the origins of differences manifesting in the transfer functions between conditions. This will provide new insights into the effects of nasal tract coupling on voice acoustics, which could in turn lead to the development of useful new tools to support clinicians in their work with hypernasality.

ICASSP 2023 - 2023 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

Intelligibility metrics are a fast way to determine how comprehensible a target signal is in a no... more Intelligibility metrics are a fast way to determine how comprehensible a target signal is in a noisy situation. Most metrics however rely on having a clean reference signal for computation and are not adapted to live recordings. In this paper the deep correlation modified binaural short time objective intelligibility metric (Dcor-MBSTOI) is evaluated with a single-channel close-talking microphone signal as the reference. This reference signal inevitably contains some background noise and crosstalk from non-target sources. It is found that intelligibility is overestimated when using the close-talking microphone signal directly but that this overestimation can be eliminated by applying speech enhancement to the reference signal.

Journal of voice : official journal of the Voice Foundation, Jan 26, 2017

At the upper end of the soprano range, singers adjust their vocal tract to bring one or more of i... more At the upper end of the soprano range, singers adjust their vocal tract to bring one or more of its resonances (Rn) toward a source harmonic, increasing the amplitude of the sound; this process is known as resonance tuning. This study investigated the perception of (R1) and (R2) tuning, key strategies observed in classically trained soprano voices, which were expected to be preferred by listeners. Furthermore, different vowels were compared, whereas previous investigations have usually focused on a single vowel. Listeners compared three synthetic vowel sounds, at four fundamental frequencies (f0), to which four tuning strategies were applied: (A) no tuning, (B) R1 tuned to f0, (C) R2 tuned to 2f0, and (D) both R1 and R2 tuned. Participants compared preference and naturalness for these strategies and were asked to identify each vowel. The preference and naturalness results were similar for /ɑ/, with no clear pattern observed for vowel identification. The results for /u/ showed no cle...

Journal of voice : official journal of the Voice Foundation, Jan 21, 2017

Soprano singers face a number of specific challenges when singing vowels at high frequencies, due... more Soprano singers face a number of specific challenges when singing vowels at high frequencies, due to the wide spacing of harmonics in the voice source. The varied and complex techniques used to overcome these are still not fully understood. Magnetic resonance imaging (MRI) has become increasingly popular in recent years for singing voice analysis. This study proposes a new protocol using three-dimensional MRI to investigate the articulatory parameters relevant to resonance tuning, a technique whereby singers alter their vocal tract to shift its resonances nearer to a voice source harmonic, increasing the amplitude of the sound produced. The protocol was tested with a single soprano opera singer. Drawing on previous MRI studies, articulatory measurements from three-dimensional MRI images were compared to vocal tract resonances measured directly using broadband noise excitation. The suitability of the protocol was assessed using statistical analysis. No clear linear relationships were...

Journal of Voice, 2016

The phenomenon of resonance tuning, whereby a singer modifies the shape of their vocal tract to i... more The phenomenon of resonance tuning, whereby a singer modifies the shape of their vocal tract to increase the acoustic power output, is commonly exploited across large pitch ranges by professional sopranos and has been observed to a lesser degree in nonexpert adult singers. This study considers the employment of two common resonance tuning techniques in experienced child singers; tuning the first vocal tract resonance to the fundamental (R1:f o) and tuning the second resonance to the second harmonic (R2:2 fo). Methods. Wide-band excitation at the subject's mouth during singing was used to measure the vocal tract resonances of three girl choristers, and vowel formant values in speech were extracted from samples of spoken text. Measured resonance values were cross-referenced with first and second harmonics for sung vowels across the subjects' ranges to identify the resonance tuning techniques employed, and these results were compared with those previously observed by others in professional adult classical singers. Results and Conclusions. There was clear evidence that the subjects employed resonance tuning techniques comparable with the strategies used by adult singers. The protocol and results presented here pave the way for further studies exploring the development of resonance tuning techniques in young soprano voices, with the potential to impact on approaches to classical singing training in the future.

ABSTRACT This paper presents a new algorithm for extracting vocal tract shape from, speech or sin... more ABSTRACT This paper presents a new algorithm for extracting vocal tract shape from, speech or singing. Based on acoustic sensitivity functions it removes the ambiguity that conventional methods suffer from. We describe acoustic sensitivity functions and how we extract the necessary formant frequencies from the acoustic waveform. Results are presented for a variety of singers both male and female singing a variety of vowels and notes. The results are good and the system not only has applications in voice training but could also be used for control of games or music synthesis.