Effects of Straw Phonation and Neutral Vowel Protocols on the Choral Sound of Two Matched Women’s Choirs

Abstract

Many choral teacher-conductors and voice professionals utilize semioccluded vocal tract (SOVT) exercises (e.g., lip trills, straw phonation) in their classrooms or studios. Research with individual singers has indicated that these techniques may increase “vocal economy,” boosting acoustic output while reducing singer effort. Recently, researchers have investigated these phenomena in choral settings, finding that choirs have maintained or increased spectral energy after straw phonation. Most chorister participants have perceived improved choral sound and vocal efficiency after the protocols. These investigations, however, have used one-group pretest-posttest designs. Therefore, results could reflect a “masterclass effect.” The purpose of this study was to compare acoustic output and listener perceptions of pre- and posttest measurements of two matched women’s choirs who engaged in (a) a straw phonation protocol or (b) an identical protocol performed on a neutral, unoccluded vowel (“ah”). Results indicated that both groups sang with more spectral energy after the protocols, and a majority of expert listeners noted these increases. However, the straw group’s increase was more than 1 dB SPL greater across the entire spectrum (0–10 kHz). Choral teacher-conductors and music teacher educators may wish to use straw phonation exercises to increase choral output and reduce vocal effort.

Keywords

semi-occluded choral pedagogy choral acoustics straw phonation vocal exercises

Vocal exercises that can be described as using a semi-occluded vocal tract (SOVT) are widely utilized by singing teachers, choral teacher-conductors, vocal performers, and voice therapists. These exercises are characterized by a partial constriction of airflow occurring somewhere between the vocal folds and the lips. This constriction can be produced by narrowing the airway in some fashion (e.g., pursed lips or holding a straw between the lips) or oscillating between an open airway and a complete obstruction of the airway (e.g., lip or tongue trill). A wide range of exercises fits this broad definition (Nix & Simpson, 2008). Speech and voice therapists have developed several formalized therapy protocols with the SOVT as a central element (Bassiouny, 1998; Laukkanen, 1992; Simberg & Laine, 2007; Stemple, Lee, D’Amico, & Pickup, 1994). Acting voice methods also utilize SOVT gestures to similar ends (Aderhold, 1963; Linklater, 1976). In the training of singers, voicing into a straw (i.e., straw phonation, Nix & Simpson, 2008); nasal consonants such as /m/, /n/, and /ŋ/ (Gregg, 1996; Nix 2016); articulatory glides such as /j/ and /ɲ/; lip trills; tongue trills; and “raspberries” are all SOVT gestures used to entrain more efficient vocal production (Nix, 1999, 2013).¹ Through “greater acoustical output with lower vibration amplitude and less forceful vocal fold tissue collision” (Nix, 2013, p. 46), singers might healthfully produce more sound with less effort.

As varied as the application of these exercises may be, they are all used for the same general purpose of eliciting increased vocal output while simultaneously easing the stresses inflicted on the vocal folds during phonation. Theoretical (Story, Laukkanen, & Titze, 2000; Titze, 2006) and human subject (Maxfield, Titze, Hunter, & Kapsner-Smith, 2015; Titze, Laukkanen, Finnegan, & Jaiswal, 2002) studies have indicated that SOVT exercises result in changes in vocal tract impedance and increases in pressures within the airway (both above and below the larynx). These changes reduce the amount of breath pressure required to initiate voicing (i.e., phonation threshold pressure) and lower the collision force applied to the vocal folds as they vibrate (Titze, 2004) while also increasing the acoustic energy created by each collision (Titze, 2004). Laukkanen, Lindholm, Vilkman, Haataja, and Alku (1996) also noted that one SOVT exercise (i.e., the bilabial fricative—voicing through a very narrow opening at the lips) reduced neck muscle activity in healthy speakers without changes to the vocal acoustic output after the semi-occlusion was subsequently removed. Such reductions in breath pressure, vocal fold collision force, and neck muscle activity combined with consistent or increased acoustic energy could be an indication of an increase in “vocal economy.”

In the broad field of vocal health, research into the effects and usefulness of SOVT exercises has increased significantly in recent years. Researchers have investigated the efficacy of several SOVT exercises as a rehabilitative tool for voice users experiencing various voice problems. Kapsner-Smith, Hunter, Kirkham, Cox, and Titze (2015) found both straw phonation and Stemple’s Vocal Function Exercises (i.e., phonating through a tightly closed /u/ or “ooh”) reduced perceived roughness in the voices of patients with functional dysphonia. Guzmán, Higueras, Fincheira, Muñoz, and Guajardo (2012) found straw phonation significantly improved several standard acoustic measures of voice quality (e.g., cepstral peak prominence, jitter, and harmonic-to-noise ratio) in a group of teachers with dysphonic voices. Guzmán et al. (2016) found similar results using Lax Vox therapy (i.e., voicing through a tube submerged in water) for subjects with functional dysphonia.

In other studies, researchers have examined the effect of SOVT exercises on the contact pattern and impact stress of the vocal folds during vibration (Verdolini, Chan, Titze, Hess, & Bierhals, 1997). These investigations, however, have been inconclusive, with some studies showing an increase in impact stress (i.e., closed quotient; Dargin, DeLaunay, & Searl, 2016; Guzmán et al., 2015) and other studies showing a decrease (Croake, Andreatta, & Stemple, 2017; Gaskill & Erickson, 2008; Guzmán et al., 2013) during a range of SOVT exercises. The discrepancy in these findings indicates a need for further study with larger participant pools.

Researchers have also investigated SOVT exercises in singing pedagogy. Dargin and Searl (2015) noted increases in sound pressure level (the acoustical correlate to singing volume) and airflow in four singers after engaging in straw phonation, lip trill, and tongue trill protocols. In a follow-up study, Dargin et al. (2016) again noted that SOVT exercises provided some acoustic benefits. In both studies, results varied in magnitude among the participants. Guzmán et al. (2013) noted increased prominence in the singer or speaker’s formant cluster region (i.e., vocal “ring”) and perceived benefits in voice quality after the protocols. The difference was greater with a narrow straw (2.5 mm × 13.7 cm) than with a tube (9 mm × 27 cm). Guzmán et al. asserted the protocols produced improved “vocal efficiency and vocal economy (more loudness without an increase of vocal loading due to increased vocal fold collision)” (pp. e31–e32).

These studies seem to indicate that SOVT exercises can improve vocal economy by reducing effort and maintaining or increasing vocal output in healthy or disordered speakers and singers. All of these investigations, however, involve measurements with individuals. Many singers receive the bulk of their singing instruction in group settings where choristers may phonate using different resonance techniques than solo singers (Ford, 2003; Rossing, Sundberg, & Ternström, 1986). Rossing et al. (1986), for example, found that male singers utilized less acoustic energy in the “singer’s formant” region when asked to sing in “choral mode.” The singer’s formant (or singer’s formant cluster) is an acoustic boost in the 2- to 4-kHz region that enables solo classical singers to carry over an orchestra (Sundberg, 1987). It is also the area in which the human ear is most sensitive (Fletcher & Munson, 1933). Listeners have tended to prefer the choral sound when choristers intentionally sang with less singer’s formant resonance (Ford, 2003) or when the spectral energy in this region was dampened because of increased inter-chorister spacing (e.g., Daugherty, Manternach, & Brunkan, 2012). Changes in vocal production related to spacing likely occurred unconsciously with variations in choristers’ ability to hear their own voices in relation to those surrounding them (self-to-other ratio; Ternström, 2003). Because of these factors, studies with individuals may not directly apply to conglomerate, choral sound.

Despite the possible differences between solo and choral singing, choral teacher-conductors and music teacher educators have long advocated the use of various SOVT exercises (Brinson & Demorest, 2014; Ehmann & Haasemann, 1981; Nesheim & Noble, 1995; Phillips, 2016; Titze & Henderson, 2015). Brinson and Demorest (2014), for example, recommended lip and tongue trills for developing efficient breath flow as well as singing with the hand over the mouth or humming to increase feelings of vocal resonance. Phillips (2016) also recommended humming and nasal consonants as a way to feel resonance and ameliorate breathy singing. Davids and LaTour (2012) recommended various SOVT exercises and noted that straw phonation could help with vocal fold closure. Titze and Henderson (2015) also advocated straw phonation during an interest session at the American Choral Directors Association national symposium, positing that it could stretch and un-press the vocal folds during warmups.

To test the efficacy of these techniques in choral settings, Manternach, Clark, and Daugherty (2017) utilized a straw phonation protocol with a small SATB choir (N =15 choristers) as they sang two Renaissance motets of differing tempi. The protocol was taken from a YouTube video produced by Ingo Titze and the National Center for Voice and Speech (Jmostrem, 2009). Because of the complexity of choral sound, we used long-term average spectrum (LTAS) analyses, which create an average of acoustic energy over a given period. Researchers have utilized this analysis technique when examining changes in choral sound related to conductor gesture (Grady, 2014), choral formation (Aspaas, McCrea, Morris, & Fowler, 2004; Morris, Mustafa, McCrea, Fowler, & Aspaas, 2007), vocal registers and dynamic levels (Morris, Ternström, LoVetri, & Berkun, 2010), and chorister spacing (Daugherty et al., 2012). LTAS analyses revealed statistically significant differences in spectral energy across the entire spectrum (0–10 kHz) and in the area where human hearing is most sensitive (approximately 2 to 4 kHz; Fletcher & Munson, 1933). Though these differences in spectral energy did not reach the threshold of a “just noticeable” difference when listening to complex sounds (i.e., 1 dB SPL; Howard & Angus, 2006), the posttest spectral energy was greater during both pieces (Manternach et al., 2017).

In another study (Manternach & Daugherty, 2017) with a more experienced SATB choir (N = 48 choristers), straw protocols did not evoke statistically significant changes in the spectrum. Most choristers, however, reported that the group sounded better (78.3%) and that they individually sang more efficiently/comfortably (73.9%) after the protocol. In a third study (Manternach & Clark, 2018), a male barbershop chorus (N =17 choristers) sang with significant differences in spectral energy (1.00 dB SPL higher in posttest) that were possibly noticeable, and most choristers who completed a follow-up survey again reported that they sang more efficiently/comfortably (62.5%) and that the chorus sounded better (85.7%) after the straw protocols. The maintenance or increase in spectral energy with perceptions of more vocal efficiency seems to align with research findings from individual singers. We suggested that teacher-conductors can use straw phonation techniques to evoke more efficient singing and increases in overall chorister vocal economy.

These investigations have all included choruses with male participants. Researchers have noted, however, that female singers in upper ranges tend to use vowel modification in lieu of singer’s formant clustering to align their singing frequency (first harmonic) with the lowest frequency of the vocal tract (first formant) for an acoustic boost (Henrich, Smith, & Wolfe, 2011; Weiss, Brown, & Morris, 2001). Consequently, straw phonation protocols may affect bass and treble choruses differently. In addition, these investigations have all utilized one-group pretest-posttest designs. Therefore, it is unclear if these changes are the result of the protocol or if they simply reflect a “masterclass effect” (i.e., placebo effect).

The purpose of this study was to investigate acoustic and perceptual changes in pre- and posttest measurements of LTAS of two matched women’s choirs as they performed from memory an unaccompanied piece prior to and after engaging in an identical protocol performed on (a) a semi-occluded vocal tract exercise (i.e., straw phonation) or (b) a neutral, unoccluded vowel (i.e., /ɑ/ or “ah”). Results from such an investigation can inform choral teacher-conductors, vocal pedagogues, and music teacher educators as they seek time-efficient ways to evoke and entrain efficient singing from choristers during warmup and voice building procedures. The following research questions guided the investigation: (1) Will there be significant changes in either choir’s overall spectral energy (0–10 kHz) as they sing prior to and after taking part in a straw phonation or neutral vowel protocol? (2) Will there be significant changes in either choir’s spectral energy in the acoustical region in which the human ear is most sensitive (2–4 kHz)? (3) Will a panel of expert listeners detect differences in the vocal energy between pre- and posttest recordings of either choir? and (4) Will spectral and listening results vary between straw phonation and neutral vowel protocols?

Method

Participants

Singer participants (N = 22) were members of two women’s choirs, one upper division and one lower division, at a small, two-year midwestern college. The directors of the two ensembles collaborated to create two different matched ensembles (n = 11 each) based on singer voice parts and their perceptions of the musical skill, vocal skill, and vocal timbre of each singer. One group served as the experimental group, which was made up of two singers assigned to the scored part for Soprano II (SII) and three singers assigned to each of the remaining sections—Soprano I (SI), Alto I (AI), and Alto II (AII). The second group served as the control group, which was made up of two singers assigned to the scored part for SI and three singers assigned to each of the remaining sections—SII, AI, and AII. Because the groups had five combined singers assigned to both the SI and SII parts, the matched sections were uneven. We opted to maintain this voicing for singer comfort and because of the repeated measures design.

Expert listener participants (N = 13) were current K–12 choral directors (n = 4), collegiate choral directors (n = 1), or graduate students in choral music education (n = 3) or choral conducting (n = 5). They were 23 to 63 years old (M = 35.4, SD = 9.7) and had 3 to 40 years (M = 13.1, SD = 10.2) of choral directing experience. All listener participants had degrees in vocal/choral music education or choral conducting and reported no diagnosed hearing loss.

Procedures

Both choirs prepared and memorized “Sweet Hour of Prayer,” a traditional 19th-century tune by William B. Bradbury. This arrangement (Hal Leonard publishing), scored for two soprano and two alto lines (SSAA voicing), was originally performed by the Anonymous 4. The brisk, 55-second piece (MM = 145–150) was part of their performance repertoire for the season.

For both groups, we utilized a prerecorded conductor to control for the conductor gestures (e.g., size, facial expression, posture, tempo) in the visual stimulus (Daugherty, 2003; Manternach, 2016). The conductor, the director of the lower-division ensemble, appeared from roughly waist height to just above the head, and his image was projected on the front wall of the rehearsal room. He conducted “Sweet Hour of Prayer” using one pulse per three-beat measure (i.e., “in one”).

Control group procedures

The recording procedures took place in the ensembles’ regular rehearsal space. On the first day of data collection (Monday, see Table 1 for timeline), the control group gathered for rehearsal and took their place in a single arc facing the front wall of the rehearsal room. They stood with their right foot on premarked strips of tape spaced 24 in. apart. The configuration conformed to the parameters of “lateral” spacing used in previous research (e.g., Daugherty, 2003) that has seemed to produce favorable chorister self-to-other ratios. The markings also ensured that participants stood in precisely the same location throughout the study protocols. The choir sang through “Sweet Hour of Prayer” two times to confirm memorization and become acquainted with the conductor cueing procedures. They then recorded the piece while following the prerecorded conductor.

Table 1.

Data Collection Timeline.

Group	Monday	Wednesday
Experimental group (straw phonation)	Straw practice session	Data collection
Control group (/ɑ/ vowel)	Data collection	No meeting

Experimental group procedures

On the same Monday, at a subsequent rehearsal, the experimental group took part in a short group rehearsal session designed to acquaint them with straw phonation protocols. In previous research (Manternach et al., 2017), chorister anecdotes reflected perceptions of difficulty in taking part in straw phonation for the first time during data collection. Therefore, we decided that a brief coaching period would be useful. At the subsequent rehearsal (Wednesday), the experimental group followed the same recording procedures that the control group had followed on the Monday rehearsal.

Straw and /ɑ/ protocol

Following the first recording of “Sweet Hour of Prayer” on the respective recording days, each group participated in a roughly 4½ -min voicing protocol. The control group performed the protocol on an unoccluded /ɑ/. The experimental group performed the protocol through a small stirring straw that was 12.75 cm long and had an opening diameter of 2.5 mm. We chose this straw because the measurements have been found to create among the highest levels of vocal tract impedance among various SOVT exercises (Maxfield et al., 2015). In addition, researchers found that a straw with a similar opening diameter evoked more robust changes in an individual singer than a tube with a larger opening (Guzmán et al., 2013).

The protocol was based on the YouTube video produced by the National Center for Voice and Speech (Jmostrem, 2009) and is similarly described in a previous study in this line of inquiry (Manternach et al., 2017). We chose this video because it was (a) produced by researchers who have investigated SOVT exercises and (b) easily accessible to choral directors, thus making the technique available to music teacher educators as well as teacher-conductors who might be interested in using it in their ensembles. The protocol began with a series of vocal glides (approximately 1 min and 50 s), each around 10 s, starting very low in the range, ascending to very high in the range, and descending gradually again to the lowest note. Next, participants completed five “accents” (approximately 1 min and 30 s; Jmostrem, 2009). These “accents” included a series of vocal pulses (i.e., “hills”) that varied in pitch and loudness as they ascended through the vocal range. After a specified number of pulses, participants then used a vocal glide to descend again to their lowest note. Participants performed accents five times, beginning with three pulses and adding one with each iteration until reaching seven pulses. Finally, participants sang a unison rendition of the “Star Spangled Banner” that left out the second repetition of the initial melody (“Whose broad stripes . . . ”). This rendition, in the key of A major, took roughly 1 min and 15 s.

After each group had completed the protocol on the unoccluded /ɑ/ vowel (control group) or through the straw (experimental group), they rechecked their standing positions, focused on the projection at the front of the room, and waited for the cue from the prerecorded conductor. They then recorded “Sweet Hour of Prayer” a second time while following the conductor.

Recording equipment

We recorded .wav audio files of the choir using a ZOOM H6 device (XY microphone attachment, 90° angle) at a 44.1 kHz sampling rate (16 bits). The microphone was located in a near-field conductor position, 10 ft. from the choir. LTAS, which are often used to measure overall choral timbre (e.g., Daugherty et al., 2012; Morris et al., 2010), provided data for pre- and posttest comparisons. We used KayPENTAX Multi-Speech Model 3700 (version 3.4.1) software to analyze the recordings. The software extracted the LTAS data for each of the two channels of the XY microphone attachment using a window analysis size of 512 points with no pre-emphasis or smoothing, a bandwidth of 86.13 Hz, and a Hamming window. This bandwidth resulted in 117 data points across the 0- to 10-kHz spectrum including 23 data points in the 2- to 4-kHz region. We subsequently calculated the mean of the two channels for graphing and statistical analyses.

Listening panel

After the acoustical analysis, 13 practicing choral directors listened to randomly ordered pairs of each group’s first 16 measures and subsequent 16 measures on AKG studio headphones (K 240 MK II, 55 ohms impedance) that connected to a preamp (Sound Devices USB Pre 2) and a Dell laptop (Latitude E7470, Core i7 vPro). We chose smaller paired excerpts to provide listeners with more immediate comparisons of each section. They listened to each pairing as many times as necessary and in any order to decide whether they heard differences in vocal energy and, if so, which excerpt evidenced greater vocal energy.

Results

Entire Spectrum

We conducted paired t-test analyses across the entire spectrum (0–10 kHz) for both the experimental and control groups. Results indicated a statistically significant difference in the overall spectrum for the experimental group, t(116) = 24.72, p < .001, d = 2.29; mean energy was 1.35 dB SPL higher across the spectrum after the straw phonation protocol (Figure 1). There was also a statistically significant difference across the overall spectrum for the control group, t(116) = 3.57, p = .001, d = 0.33; mean energy was 0.40 dB SPL higher across the spectrum after the /ɑ/ protocol (Figure 2). The difference for the experimental group exceeded 1 dB SPL while the difference for the control group did not.

Figure 1.

Pre- and posttest spectral energy, 0 to 10 kHz, for the experimental (straw phonation) group.

Figure 2.

Pre- and posttest spectral energy, 0 to 10 kHz, for the control (/ɑ/ vowel) group.

2- to 4-kHz Region

We also conducted paired t test analyses in the 2- to 4-kHz region. Results indicated a statistically significant difference in the experimental group, t(22) = 11.02, p < .001, d = 2.30; mean spectral energy was 1.33 dB SPL higher after taking part in the straw phonation protocol. This difference was nearly identical to the mean differences across the entire spectrum. There was also a statistically significant difference in the control group, t(22) = 11.03, p < .001, d = 2.30; mean spectral energy was 0.89 dB SPL higher after the /ɑ/ protocol. This increase was just more than double than the increase across the entire spectrum.

Listening Panel

A panel of 13 practicing choral directors listened to randomly ordered paired recordings of each group’s opening 16 measures and subsequent 16 measures. Nine of the 13 listeners (69.2%) reported a difference in the overall vocal energy of the straw phonation group’s first 16 measures. Of those perceiving a difference, 6 (46.2%) noted more vocal energy after the straw protocols, and 3 (23.1%) noted more vocal energy before the protocols. Nine listeners (69.2%) also reported a difference in the subsequent 16 measures. Seven (53.8%) noted more vocal energy after the straw protocols, and 2 (8.7%) noted more vocal energy before the protocols.

Seven of the 13 listeners (53.8%) perceived a difference in the overall vocal energy of the control group’s first 16 measures. Of those reporting a difference, five (38.5%) noted more vocal energy after the /ɑ/ vowel protocols, and two (15.4%) noted more vocal energy before the protocols. Eleven of the 13 listeners (85.6%) also perceived a difference in the subsequent 16 measures. Nine (69.2%) noted more vocal energy after the straw protocols, and two (15.4%) noted more vocal energy before the protocols. Taken together, listeners noted more vocal energy in the posttest 14 times (53.8%) in the control group and 13 times (50.0%) in the straw group. They noted higher vocal energy in the pretest only five (19.2%) and four times (15.4%), respectively.

Discussion

The purpose of this study was to investigate acoustic and perceptual changes in pre- and posttest measurements of LTAS of two matched women’s choirs as they performed from memory an unaccompanied piece after engaging in an identical protocol performed on (a) a semi-occluded vocal tract exercise (i.e., straw phonation) or (b) a neutral, unoccluded vowel (i.e., /ɑ/). Primary findings indicate that both groups displayed higher mean spectral energy across the entire spectrum (Research Question 1) and in the 2- to 4-kHz region (Research Question 2) after they took part in the protocols. Listeners reported increases in posttest recordings at approximately the same rate (Research Question 3). However, the straw phonation group’s increase was nearly 1 dB SPL greater than the control group (Research Question 4). These data are specific to the two ensembles in the current study and cannot be generalized. However, results seem to dovetail with previous investigations of individuals and ensembles who have engaged in SOVT exercises (e.g., Dargin & Searl, 2015; Guzman et al., 2012; Manternach & Clark, 2018; Manternach et al., 2017). Should these data continue to align, there may be several implications for researchers, choral teacher-conductors, and music teacher educators.

Both the control group and the straw phonation group experienced boosts in spectral energy after their protocols, and a majority of listeners in this study perceived those boosts. However, the increase was nearly 1 dB SPL greater in the experimental group than in the control group. These results are consistent with findings in previous choral and solo literature that suggest vocalists may experience an increase in vocal output after engaging in straw phonation. As previous research has indicated, SOVT exercises have evoked decreased phonation threshold pressure (Titze, 2006), reduced neck muscle activity (Laukkanen et al., 1996), and perceptions of easier voicing for choristers (Manternach & Clark, 2018; Manternach & Daugherty, 2017). Though we focused on acoustic and listener data, it seems feasible that our singers experienced these physiological benefits as well. Therefore, our results could be the strongest evidence to date suggesting that SOVT exercises may encourage vocal efficiency and economy in choral settings.

The increase in mean spectral energy in the control group was comparable to the increases experienced by a straw phonation group in a previous study (Manternach et al., 2017). It is possible that this change took place because of the /ɑ/ vowel protocol. However, participants in the previous study took part in a warmup protocol prior to engaging in the experimental procedures. In the present investigation, the singers performed each piece two times but did not engage in any systematic vocalises or warmup procedures prior to the experimental protocols. The control group’s boost of 0.40 dB SPL, therefore, may be the result of being slightly more “warmed up” after taking part in the protocols. Regardless, the boost in spectral energy for the straw phonation group was nearly 1 dB SPL higher than for the control group. This result may indicate that the SOVT exercise was a more efficient warmup than the neutral vowel. Future researchers may wish to test this possibility by varying warmup procedures in similar studies.

In this investigation, the control group experienced a larger boost in the 2- to 4-kHz range (0.89 dB SPL) than across the entire spectrum (0.40 dB SPL). This result may indicate that the protocol led to voicing that was more similar to that of solo singers, resulting in increases in the “singer’s formant cluster” region. Some would advocate this voicing technique in choirs (Fagnan, 2005). Most systematic research, however, indicates that choral singers generally avoid such a boost (Ford, 2003; Rossing et al., 1986). In the straw phonation group, however, the increases in the overall spectrum and in the 2- to 4-kHz region were nearly identical. Therefore, the straw phonation may have evoked a boost in overall energy without significant changes in the overall timbre.

Limitations and Future Research

Future investigations may continue to benefit from a combination of acoustic results and listener perceptions. Listeners may detect differences in tuning or other vocal characteristics that may not appear in LTAS analyses. In addition, researchers may wish to include a survey regarding perceptions of vocal efficiency after each of the protocols. In previous investigations, choristers perceived that they sang more efficiently and that the choir sounded better after the straw phonation protocols. A survey of both an experimental and a control group would help illuminate whether such differences are related to the independent variable or are simply a “masterclass effect.”

We modeled our straw protocol after one that is readily available to choral directors, which resulted in the approximately 4½-min session. It is possible, however, that a longer treatment or one that occurs over time might elicit more robust differences. Our control group also performed the protocol on an /ɑ/ vowel to provide a relevant comparison. Future researchers might add a control group that remains silent between pre- and posttest measurements.

We decided to collect data on consecutive rehearsal days (Monday and Wednesday) to ensure that data collection took place at precisely the same time of day and in the same space for both groups. However, it is possible that there was a history effect or a change based on the day of the week. Future researchers may wish to conduct the experimental procedures on the same day, one after the other. Conversely, they might reverse order of the data collection.

Our LTAS analyses detected differences between takes in low frequencies that are often associated with environmental noise. It is feasible that choristers would unconsciously change their vocal production in response to these changes. Because the recording space was the normal rehearsal room for these choristers, they may already have been accustomed to these changes. Nonetheless, future researchers may wish to account for environmental noise by recording in a sound-controlled space or one that has the air handling systems temporarily disabled.

In addition, we opted to use straws that create high levels of impedance (Maxfield et al., 2015) and that were similar to the straw recommended by Titze in his YouTube instructional video (Jmostrem, 2009). Nix (2008) has suggested, however, that voice instructors might wish to introduce the technique with a larger straw and move to smaller sizes as singers become comfortable with the increased pressure during voicing. Researchers may wish to employ this tactic and perhaps allow singers to choose their preferred straw. More research utilizing these varied straw sizes or using (a) other choirs, (b) varied rehearsal/performance spaces, (c) contrasting choral excerpts, (d) varied levels of familiarity with straw phonation techniques, (e) changes in chorister spacing, and (f) simultaneous physiological measurements from individual choristers could further understanding of the effects of SOVT exercises in choral settings.

Finally, we asked participants to perform the same piece before and after the protocols. We did not, however, give instructions as to how they were to sing. Acoustic changes therefore may have been passive. In addition, it is possible that the pressure changes and resulting changes to vocal fold vibration may lead to increased vocal facility. Researchers may wish to ask singers to complete various vocal exercises to test whether straw phonation protocols may temporarily entrain improvements in vocal technique.

Implications for Music Teacher Educators

Paired with previous studies that indicate reduced phonation threshold pressure and neck muscle activity after SOVT exercises, one might speculate that straw phonation protocols can lead to increased vocal efficiency and economy, namely, increased vocal output with reduced effort. If such is the case, choristers may have been able to use less voicing effort while producing more energy in the conglomerate, choral sound. Teacher-conductors and music teacher educators may therefore wish to include SOVT exercises in their voice building and warmup procedures. Such exercises could include using the glides and “accents” utilized in this protocol during vocal warmups. Teacher-conductors may also wish to develop their own protocols or ask choristers to sing their respective parts on excerpts from their performance literature. It seems feasible that doing so could help choristers to develop more efficiency or vocal facility in the context of their repertoire. If such is the case, the increases in vocal economy and possible acoustic benefits may prove to be a time-efficient technique to evoke and entrain efficient singing in the classroom and the concert hall.

Footnotes

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Notes

ORCID iD

Jeremy N. Manternach

Author Biographies

Jeremy N. Manternach is assistant professor of music education at the University of Iowa. His research is related to vocal and choral pedagogy, voice science, and vocal and choral acoustics.

Matthew Schloneger is assistant professor of voice at Friends University. His research interests include vocal pedagogy, vocal efficiency and health, and voice use.

Lynn Maxfield is associate director of the National Center for Voice and Speech at the University of Utah. His research is related to vocal health, acoustic assessment of the singing voice, and motor skill acquisition in singers.

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