The intensities of vowels and plosive bursts and their impact on text intelligibility in singinga).

In classical singing, there are often problems with the intelligibility of sung text. The present study aims to test the hypotheses that (1) in loud operatic singing, compared with speaking, the intensity of voiceless plosives increases less than the intensity of vowels, leading to poorer recognition of plosives; and (2) pronouncing the plosive bursts with greater intensity improves their recognition. The acoustic analysis of nine opera arias in Italian from the Classical and Romantic periods performed by ten classically trained singers showed that the average difference in the intensity of vowels when sung and spoken was 14.6 dB [standard deviation (SD) = 7.2 dB], while the difference in the intensity of voiceless plosive bursts was only 6.6 dB (SD = 6 dB). In a perception test with 73 participants, increasing the intensity of the plosive bursts generally improved the recognition of plosives in the sung /a-plosive-a/ sequences, but mainly when reverberation and/or pink noise imitating instrumental accompaniments were added to the stimuli. At the same time, recognition of plosives was often better than chance even when the plosive burst was missing and replaced by silence.

Amplitude Effects of Vocal Tract Resonance Adjustments When Singing Louder.

In the literature on vocal pedagogy we may find suggestions to increase the mouth opening when singing louder. It is known that sopranos tend to sing loud high notes with a wider mouth opening which raises the frequency of the first resonance of the vocal tract (fR1) to tune it close to the fundamental. Our experiment with classically trained male singers revealed that they also tended to raise the fR1 with the dynamics at pitches where the formant tuning does not seem relevant. The analysis by synthesis showed that such behaviour may contribute to the strengthening of the singer's formant by several dB-s and to a rise in the centre of spectral gravity. The contribution of the fR1 raising to the overall sound level was less consistent. Changing the extent of the mouth opening with the dynamics may create several simultaneous semantic cues that signal how prominent the produced sound is and how great the physical effort by the singer is. The diminishing of the mouth opening when singing piano may also have an importance as it helps singers to produce a quieter sound by increasing the distance between the fR1 and higher resonances, which lowers the transfer function of the vocal tract at the relevant spectral regions.

Phonatory Strategies of Male Vocalists in Singing Diatonic Scales With Various Dynamic Shapings.

This work aimed to investigate glottal adduction in the case of the singing of diatonic D major ascending scales with different dynamic shapings on vowel [a:] by 10 classically trained male singers. The parameters obtained by inverse filtering-closed quotient (CQ), normalized amplitude quotient (NAQ), and the level difference between the first two partials of the glottal flow waveform spectrum (H1-H2)-all indicated statistically significant systematic changes when singers sang (1) with habitual dynamics without intentional dynamic changes; (2) with sempre crescendo from piano to forte; and (3) with sempre diminuendo from forte to piano. Adduction on average was lower if the tone with the same pitch was sung piano compared with when it was sung forte. The piano tones with the limit of one and the same dynamic task were sung with lower adduction on average compared with one octave higher or lower tones sung forte, although here the agreement between different parameters was poorer and the individual variability was greater. There was only a moderate negative correlation between CQ and NAQ (r = -0.41) but a strong negative correlation between CQ and H1-H2 (r = -0.8). CQ showed a moderate positive correlation with sound level but no significant correlation with pitch. NAQ showed a strong and significant positive correlation with pitch but not with sound level (except when it was calculated only at constant pitch). Some of the most experienced singers used quite high glottal adduction levels, questioning the concept of whether flow phonation is always the favorite classical style.

Timbre-induced pitch shift from the perspective of Signal Detection Theory: the impact of musical expertise, silence interval, and pitch region.

The paradigm of Signal Detection Theory (SDT) was used to analyze the ability of professional pianists (N = 16) and string players (N = 15) to discriminate small F0 differences between consecutive musical tones, presented in pairs, with identical and with different (bright and dull) timbres. The sensitivity (d') and response bias (c) were heavily dependent on the timbral arrangement of the pairs of tones (the "comparable tones"), which can be interpreted as the influence of timbre-induced pitch shift on F0 discrimination. The participants were somewhat biased to "miss" signals when comparable tones had identical timbres and to make "false alarms" when the tones had different timbres. The d' was lowest when the tones with a lower F0 in those stimulus-pairs containing tones with different timbres had a brighter timber, and highest when both tones had bright timbre. On average, the string players had a somewhat higher d' and their perception was slightly less influenced by timbre-induced pitch shift when compared to the pianists. Nevertheless, the dependence of d' and c on the timbral arrangement of the tones was registered in the case of all the participants at all the investigated pitch regions around D#3, D4, and C#5. Furthermore, the presence of a silence of 3.5 s-a silence interval-between the tones to be compared had an impact on both d'- and c-values as well as on the degree of vulnerability to timbre-induced pitch shift.

The timbre of the voice as perceived by the singer him-/herself.

Fifteen professional singers sang simple vocal exercises at different pitches. The sung excerpts were recorded, and seven modified versions were created from each recording. The modifications were then played to the participant and (s)he had to assess the similarity of these stimuli to the perception of his/her own voice during the act of singing. Participants rated as most similar those stimuli which were modified by the filter whose frequency response most closely resembled a trapezoid, which was created by taking into account 1) the diffracting air conduction component from the mouth of the singer to his ear channel, 2) the bone conduction component, and also 3) the influence of the stapedius reflex on the sensitivity of his/her auditory system.

Mistuning in two-part singing.

This research describes the strategy of singers in reacting to the pitch deviation from equally tempered (ET) value in their ensemble partner's part in singing two-part a cappella music, and the ability of professional musicians to identify such deviations. Professional singers preferred to maintain the purity of melodic intervals in their own part and to ignore the occurring harmonic mistuning with their deviating ensemble partner. In multi-part singing, the musical interval perception ability of the singers is more finely honed for production than it is for perception, which can be explained by the enhancing effect of the memory of how to vocally produce the intervals, available only in the process of singing.

The perception of 'forward' and 'backward placement' of the singing voice.

Singing teachers sometimes characterize voice quality in terms of 'forward' and 'backward placement'. In view of traditional knowledge about voice production, it is hard to explain any possible acoustic or articulatory differences between the voices so 'placed'. We have synthesized a number of three-tone melodic excerpts performed by the singing voice. Formant frequencies, and the level and frequency of the singer's formant were varied across the stimuli. Results of a listening test show that the stimuli which were perceived as 'placed forward', correlated not only with higher frequencies of the first and second formants, but also with the higher frequency and level of the singer's formant.

Where is a singer's voice if it is placed "forward"?

Singing teachers sometimes characterize voice quality in terms of "forward" and "backward" placement. In view of our traditional knowledge about voice production it is hard to explain any possible acoustic or articulatory differences between the voices so "placed." The analysis of the teachers' expert opinions demonstrates that, in general, a voice placed "forward" indicates a desirable quality that students should attain by the end of their studies. Productions that were perceived as "forward" and "backward" were selected from the listening test. The acoustic analysis of those productions reveals that the voice quality in the case of "forward" placement correlates with higher frequencies of the second (F2) and third (F3) formants, as well as with a more salient "singer's formant" in the voice. The five basic vowels were included in the investigation.