Measurement of formant frequencies and bandwidths in singing

Perception of Vibrato by Professional Voice Teachers: A Pilot Study

OBJECTIVES

Voice teachers and clinicians often use vibrato characteristics as auditory-perceptual cues for giving functional instructions. Historical texts also point to the use of vibrato characteristics as a diagnostic tool as far back as the 18th century. This study investigates the relationship between vibrato rate and vibrato extent, and the auditory-perceptual ability of professional voice teachers to assess the vibrato rate of a synthesized singing voice.

METHODS

Thirty-five professional voice teachers completed a Visual Sort and Rate task with 20 synthesized singing samples that systematically varied in both vibrato rate (Vrate) and vibrato extent (Vext). Two generalized linear mixed effects models and one linear model were designed.

RESULTS

Both Vrate and Vext were found to be significantly associated with the perception of Vrate as well as with the accuracy of perceptual judgments. Neither listener age, nor amount of teaching experience were significant predictors of perceptual accuracy. Inter-rater agreement for the entire sample set was moderate and intra-rater reliability for samples with identical Vrate (but differing Vext) was found to be negligible.

CONCLUSIONS

While professional voice teachers have a skilled ability to discern nuanced auditory-perceptual vocal characteristics such as vibrato, in this study, samples with an identical Vrate, but for which the Vext differed seemed to demonstrate a high amount of listener rating error and variability. As such, it seems that both Vrate and Vext may play a role in the perception of vibrato rate.

Towards a Vocal and Acoustic Description of Kapa Haka

OBJECTIVE

The purpose of this study is to analyze the voice used in kapa haka, a contemporary indigenous vocal performance from New Zealand, which includes the well-known haka. This is the first study of its kind and is a preliminary investigation into the vocal and acoustic description of kapa haka. A significant goal of this study is to contribute ideas and potential definitions of vocal qualities to the community of kapa haka trainers that were specific to the genre. This strengths-based project raises up these vocal practices as legitimate and authentic colors within a vocal tradition that has seen generational learning disrupted by colonial interventions and is now flourishing within the community.

METHODS

Eight kapa haka performers (three females, five males) were involved in the study, they were all experienced performers; furthermore, two had formal classical voice training. They were individually recorded speaking and performing three different genres of kapa haka (mōteatea, waiata, and haka); all recordings were in te reo Māori (the Māori language). In addition, electroglottograph (EGG) signals were collected. An auditory-perceptual evaluation of the kapa haka voice was completed by three singer-researcher-pedagogues familiar with Western and non-western genres of singing. They all have experience appropriately collecting and analyzing data from indigenous communities, and they all understand the sociopolitical context of the vocal genre within the local colonial history. A specific evaluation instrument was created, and the results were validated. The acoustic and time-aligned EGG data was annotated at the phoneme level, and the signal analysis was performed in MATLAB. Averaged EGG pulses from /a/ segments were investigated, along with long-term average spectrums of the performances obtained from both the audio signal and the EGG signals.

RESULTS

The perceptual analysis suggests the biggest difference in vocal styles was between the haka and the other two genres (and speech). The acoustic and EGG results support these findings.

CONCLUSIONS

Common characteristics, perceptually and acoustically, were identified in the kapa haka performance styles across the eight performers.

Sound production by singing humpback whales

Sounds from humpback whale songs were analyzed to evaluate possible mechanisms of sound production. Song sounds fell along a continuum with trains of discrete pulses at one end and continuous tonal signals at the other. This graded vocal repertoire is comparable to that seen in false killer whales [Murray et al. (1998). J. Acoust. Soc. Am. 104, 1679-1688] and human singers, indicating that all three species generate sounds by varying the tension of pneumatically driven, vibrating membranes. Patterns in the spectral content of sounds and in nonlinear sound features show that resonating air chambers may also contribute to humpback whale sound production. Collectively, these findings suggest that categorizing individual units within songs into discrete types may obscure how singers modulate song features and illustrate how production-based characterizations of vocalizations can provide new insights into how humpback whales sing.

The Interplay between Glottis and Vocal Tract during the Male Passaggio

The transition between 'chest' and 'head' register is essential for male opera singers in order to reach the higher pitches. The 'passaggio', which is a scale passage where this transition takes place, but also a maneuver of register equalization, is typically difficult to learn. Studies on parameters for a definition of this transition are restricted to a small number of singers so far. Audio, electroglottographic, and equivalent subglottic pressure signals of 11 male opera singers were recorded while singing scales on open back vowels and passing the register transition. A spectrum analysis of the audio signal revealed that the second harmonic (H2) dominates in 'chest', resonated by the first formant (F1), together with the fourth harmonic (H4), supported by the second formant (F2). During the passaggio, H2 level decreases because it loses the resonance of F1, while the third harmonic (H3) gains the resonance of F2. At this point the H4 level drops because that harmonic is no longer supported by F2. The transition from 'chest' to 'head' register is marked by characteristic changes in the amplitude patterns of the partials H2, H3, and H4, and the frequency progressions of the first two formants, defining an objective distinction between the two registers.