The Vocal Tract Organ: A New Musical Instrument Using 3-D Printed Vocal Tracts

The Dynamic Effect of the Valleculae on Singing Voice - An Exploratory Study Using 3D Printed Vocal Tracts

BACKGROUND AND OBJECTIVES

The valleculae can be seen as a pair of side branches of the human vocal tract like the piriform fossae. While the acoustic properties of the piriform fossae have been explored in detail, there is little evidence of full exploration of the acoustic properties of the valleculae. A recent investigation (Vampola, Horáček, & Švec, 2015), using a finite element model of a single vowel /a/, suggests that the valleculae created two antiresonances and two resonances in the high frequency region (above 4kHz) along with those produced by the piriform sinuses. In the current study, we investigate, in multiple vowels, the acoustic influences of the valleculae in singing voice, using 3-D printed vocal tracts.

METHOD

MRI data were collected from an operatic tenor singing English vowels /a/, /u/, /i/. The images of each vowel were segmented and edited to create a pair of tracts, where one is the original and one had the valleculae digitally removed.The printed tracts were then placed atop a vocal tract organ loudspeaker, excited by white noise. Recordings were made with a microphone placed in front of the mouths of the tracts, to measure their frequency responses.

RESULTS

Dimensional changes were observed in valleculae of different vowels, with the long-term average spectra of the recordings illustrating clear differences between the frequency responses of the va-nova (valleculae - no valleculae) pairs, which varies with vowels.

CONCLUSION

The experiment demonstrates the dynamic¹ nature of the shapes of the valleculae in the human vocal tract and its acoustic consequences. It provides evidence that the valleculae have similar acoustic properties to the piriform fossae but with larger variations, and in some cases can influence acoustically the frequency region below 4kHz. The results suggest that large volume valleculae have the potential to impede to some extent the acoustic effect of the singers formant cluster and small valleculae may do the reverse. Since the volume of the valleculae is observed to be largely dependent on tongue movement and also with changes to the uttered vowel, it can be assumed that the high frequency energy, including that within the singer's formant region, could be vowel dependent. Strategies to control valleculae volumes are likely to be highly relevant to voice pedagogy practice as well as singing performance.

An Investigation in the Measurable Differences between Pitch Perception in the Voice and Pitch Perception of External Sound Sources

OBJECTIVES

Pitch perception is an important part of accurate singing. Therefore, accurate singing requires the ability to accurately assess the pitch in one's own voice.There are two objectives of this study the first was to investigate whether there is a measurable difference in perceived pitch in one's voice to the pitch one perceives from an external sound source. The second, to measure the effects of occlusion on pitch accuracy over a melodic phrase.

STUDY DESIGN

We recruited 16 participants for this study. The study that was designed to investigate the perceptual difference was split into two parts. The first is a one-to-one pitch matching test where they would recreate a pitch with singing and matching external pitches. The second was singing the familiar song 'Happy Birthday' which was used to measure pitch accuracy over a melodic phrase and to measure the effects of occlusion on pitch accuracy while singing.

METHODS

The one-to-one study involved singing back a series of 5 notes to a set vowel which were the same 5 notes used when matching them to a series of possible pitches on the button test. The melodic test was to sing 'Happy Birthday' 3 times, the first normally, the second wearing headphones to occlude the ear to reduce air conductive hearing and the third time with white noise to mask all hearing.

RESULTS

The results showed a higher accuracy of pitch matching with external sounds over using their voice, and some form of occlusion (wearing headphones or headphones with white noise) showed the version with higher pitch accuracy.

CONCLUSIONS

The results of this study showed that there was improved pitch accuracy when comparing two external sounds in pitch and when singing occlusion of some form improved pitch accuracy. This could suggest a difference when recreating pitch between the voice and matching external sound sources. Furthermore, with the improvements shown from occluding the ears, it could further suggest a difference in pitch perception abilities between the voice and external sound sources. This could have implications of improving pitch accuracy in a studio environment.

The Role of Vibrato in Group Singing: A Systematic Review

INTRODUCTION

Arguably one of the most controversial features of the singing voice, especially in a choral context, is the phenomenon of vibrato. Numerous pedagogical articles, mostly written by experienced choral singers or directors, discuss the importance of vibrato, sharing anecdotal insights about its control (often advocating reduction) in choral blend and vocal health.

OBJECTIVES

This systematic review aims to identify the main questions posed in the empirical study of vibrato during group singing, and how they have been addressed to date through empirical investigations.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was employed for this review. The review team consisted of the two authors. A data extraction form was designed to capture information about the participants (including age, gender, music and singing experience), study methods, experimental procedures, outcome measures, and statistical findings.

RESULTS

Seventeen studies were included in the review and revealed that (a) relatively few empirical investigations have studied vibrato in vocal ensembles; (b) the majority focused on vibrato production rather than perception; (c) methodological approaches include Synthesis, Multi-track recordings, Stereo/Binaural recordings, and Lx/Contact recordings; and (d) the studies focused on the main themes of Adjustment, Identification, Interaction, Intonation, and Style.

CONCLUSION

With the current body of literature, it is not possible to draw general conclusions around vibrato behavior during group singing. However, the review highlights the main subareas of interest and valuable methods which have been established and through which future research can collectively shed further light on the role of vibrato in choral singing.

Developmental History of the Vocal Tract Organ

OBJECTIVES

The Vocal Tract Organ has had a number of iterations resulting from advances in available technology as well as requirements of perceptual experiments and performance paradigms. The objective of this paper is to relate the development history of the Vocal Tract Organ from the original vision to what it is today as a modern version of the Vox Humana pipe organ stop for application in voice production and perception research.

STUDY DESIGN

Descriptive METHODS/DESIGN: The latest Vocal Tract Organ is a polyphonic eight-channel eight-stop one manual Vocal Tract Organ that enables tab stop selected three-D printed vocal tracts to be used to create sound. This version includes eight stops (four for female vowel oral tracts and four for male vowel oral tracts). The stops are implemented using conventionally engraved pipe organ stop tabs labeled "Vox Humana Female" or "Vox Humana Male" followed by the three-D printed vowel: "EE", "AH", "ER" or "UU." This is described alongside the development stages from which it emerged and covers all previous versions of the Vocal Tract Organ. At the heart of the latest instrument is a Bela BeagleBone Black with a Bela cape audio expander board which incorporates eight 16-bit audio outputs at 44.1 kHz sampling rate (earlier versions based on the Arduino Mega board were limited to 8-bit audio at an audio sampling rate of 16.384 kHz which limited the overall output spectrum). The latest Vocal Tract Organ is programmed using the audio graphical programming language Pure Data which is directly compatible with the Bela system. The Pure Data patch creates eight larynx outputs at the pitches set by the keys depressed on the keyboard and these are routed to Vocal Tract Organ loudspeakers with three-D printed vocal tracts attached.

RESULTS

The Bela system has enabled real-time synthesis of eight-note polyphonic sounds to eight separate three-D printed vocal tracts, each being selectable via an organ tab stop switch. The instrument has been cased in a purpose-designed and built prototype laser-cut enclosure that incorporates the eight tab stops, a MIDI keyboard input, a pipe organ style swell (volume) pedal connection, four stereo (eight channels) audio amplifiers and terminal connections for the eight loudspeakers.

CONCLUSIONS

The Vocal Tract Organ functions as a musical instrument for performance and as an instrument for vowel and pitch perception research. Implementing it with the Bela family of processors allows for low audio latency of 1 ms and rapid prototyping due to being able to program directly with the high-level graphical audio programming language, Pure data (Pd).

The Psychological Education Strategy of Music Generation and Creation by Generative Confrontation Network under Deep Learning

In order to study the role of generative adversarial network (GAN) in music generation, this article creates a convolutional GAN-based Midinet as a baseline model through the music generation process and creative psychological education and GAN principle. Additionally, it proposes a music generation model based on music theory rules and a chord-constrained GAN dual-track music generation model. Based on this model, a deep chord gated recurrent neural generative adversarial network (DCG_GAN) is proposed. The generated melodies are evaluated in both subjective and objective directions. The results show that the three evaluation indicators of DCG_GAN have the highest scores in the subjective evaluation. The average score given by ordinary listeners reaches 3.76 points, and the professional score reaches 3.58 points, which are 0.69 and 1.31 points higher than the baseline model, respectively. In the objective evaluation, DCG_GAN is improved by 8.075% in empty bars rate (EBR). The UPC (num_chroma_used) evaluation index value of the DCG_GAN model is improved by 0.52 compared with the baseline model. The qualified note ratio (QNR) evaluation index value is improved by up to 4.46% among the five audio tracks. The proposed overall style-based music generation model has superior performance in music generation. Both subjective and objective evaluations show that the generated music is more favored by the audience, indicating that the combination of deep learning and GAN has a great effect on music generation.

Synthesis of a Vocal Sound from the 3,000 year old Mummy, Nesyamun 'True of Voice'

The sound of a 3,000 year old mummified individual has been accurately reproduced as a vowel-like sound based on measurements of the precise dimensions of his extant vocal tract following Computed Tomography (CT) scanning, enabling the creation of a 3-D printed vocal tract. By using the Vocal Tract Organ, which provides a user-controllable artificial larynx sound source, a vowel sound is synthesised which compares favourably with vowels of modern individuals.