Laryngoscopic, acoustic, perceptual, and functional assessment of voice in rock singers

Original Paper Folia Phoniatr Logop 2013;65:248–256 DOI: 10.1159/000357707 Published online: March 18, 2014 Laryngoscopic, Acoustic, Perceptual, and Functional Assessment of Voice in Rock Singers Marco Guzman a Macarena Barros c Fernanda Espinoza c Alejandro Herrera c Daniela Parra c Daniel Muñoz b Adam Lloyd d a School of Communication Sciences and b Faculty of Medicine, University of Chile, and c School of Communication Sciences, Andres Bello National University, Santiago, Chile; d Voice Care Center, Ear, Nose, Throat, and Plastic Surgery Associates, Orlando, Fla., USA Key Words Rock singing · Growl voice · Falsetto · Singing voice · Singing Voice Handicap Index · Laryngoscopy · Acoustic analysis · Hyperfunction Abstract Objective: The present study aimed to vocally assess a group of rock singers who use growl voice and reinforced falsetto Method: A group of 21 rock singers and a control group of 18 pop singers were included Singing and speaking voice was assessed through acoustic, perceptual, functional and laryngoscopic analysis Results: No significant differences were observed between groups in most of the analyses Acoustic and perceptual analysis of the experimental group demonstrated normality of speaking voice Endoscopic evaluation showed that most rock singers presented during singing voice a high vertical laryngeal position, pharyngeal compression and laryngeal supraglottic compression Supraglottic activity during speaking voice tasks was also observed However, overall vocal fold integrity was demonstrated in most of the participants Slightly abnormal observations were demonstrated in few of them Singing voice handicap index revealed that the most affected variable was the physical sphere, followed by the social and emotional spheres Conclusions: Although growl voice and reinforced © 2014 S Karger AG, Basel 1021–7762/14/0655–0248$39.50/0 E-Mail karger@karger.com www.karger.com/fpl falsetto represent laryngeal and pharyngeal hyperfunctional activity, they did not seem to contribute to the presence of any major vocal fold disorder in our subjects Nevertheless, we cannot rule out the possibility that more evident vocal fold disorders could be found in singers who use these techniques more often and during a longer period of time © 2014 S Karger AG, Basel Introduction Voice quality in singing is affected by both laryngeal and vocal tract configuration The sound produced by the larynx is in turn determined by the vibratory patterns of the vocal folds These patterns vary depending on vocal registers (vocal fry, modal, falsetto, whistle), mode of phonation (pressed, normal, flow, breathy and whisper) as well as singing style (belting, opera, rock, etc.) [1] Modifications of vocal tract configuration are important not only to produce phonetic-articulatory features, but also because it is an important way to shape the vocal quality Particularly, the lower vocal tract structures (epilaryngeal tube, pyriform sinuses and hypopharynx) seem to play a crucial role in the quality of the singing voice Earlier studies have reported that the lower part of the vocal tract changes depending on the style of singing In clasMarco Guzman University of Chile, School of Communication Sciences Av Independencia 1027 Santiago (Chile) E-Mail guzmanvoz @ gmail.com sical singing, wide pyriform sinuses and a wide hypopharynx, as well as a narrow epilaryngeal tube have been observed [2, 3] According to Sundberg [4, 5], the area ratio between these two last structures would be the main explanation for the singer’s formant cluster On the other hand, during belting (singing technique used in pop styles, musical theater and others) a narrow hypopharynx, pyriform sinuses and epilaryngeal tube have been observed [4, 5] Moreover, in different singing styles it is common to find vocal sounds that would probably be categorized as pathological vocal qualities if they were produced by nonsingers during conversational voice usage However, these sounds are typically used as expressive and stylistic vocal resources by some contemporary commercial music singers One of these vocal resources is the so-called growl voice, which is commonly used in jazz, blues, pop, gospel and rock among others [6, 7] Moreover, similar productions have been found in ethnic singing from Brazil, Japan and South Africa [8] When this vocal resource is used in rock, it is also called death growl, death metal vocals, guttural vocals, death grunts, unclean vocals, and harsh vocals [9] Perceptually, the growl voice is similar to other types of vocal qualities such as roughness and hoarseness, which are considered perceptual signs of voice disorders Nevertheless, the growl voice is always a vocal effect or expressive emphasis and is typically not a permanent way to produce voice [10] Even though some singers use growl voice extensively during a song, it is usually not found in normal speaking voice phonation [11] According to Sakakibara et al [12] growl voice is produced through the simultaneous vibration of the vocal folds and laryngeal supraglottic structures The vocal folds vibrate periodically and the aryepiglottic folds generate subharmonics These subharmonics have also been found in other studies [13–15] A radiologic study showed that during growl voice production the larynx rose to the fourth vertebra and there was a large anterior-posterior (A-P) laryngeal constriction [12] In addition, some subjects demonstrated vibration of both right and left aryepiglottic folds in phase, whereas in other singers the phase was slightly different and in some instances aryepiglottic vibration was completely aperiodic and unstable An important group of performers that commonly use growl voice are rock singers, specifically in some rock subgenres such as screamo, thrash metal, nu metal, black metal, heavy metal, death metal, and hardcore punk [16] Rock singers not only use growl voice as part of their vocal technique, but also many other vocal resources such as the reinforced falsetto The naive falsetto (falsetto with- out training) is characterized by a decreased degree of glottal adduction, a reduction in amplitude of the electroglottographic signal which may come from a reduction of the contact surface area between the vocal folds, which could be related to a reduction in the thickness of the vocal folds compared to modal register [17–19] The reinforced falsetto usually presents a greater glottal adduction, and hence sounds louder, brighter and has more harmonic energy in the high spectral region (2–5 kHz) than naive falsetto [20] Musical styles where singers may use reinforced falsetto are: blues, glam rock, epic metal, soul, etc The reinforced falsetto in contemporary commercial music is usually associated with a shortening of the vocal tract and a very open mouth configuration Perceptually, it may sound pressed and similar to screaming [20] Since both growl voice and reinforced falsetto are probably produced with laryngeal and vocal tract constrictions, they could be labeled as vocal resources based on hyperfunctional vocal activity, which in turn might be potentially harmful to the phonatory mechanism Nevertheless, there are no empirical studies supporting this assumption The present study aimed to perceptually, acoustically, functionally, and laryngoscopically assess a group of rock singers who use growl voice and/or reinforced falsetto In particular, the question was explored of whether or not frequent use of growl voice and reinforced falsetto in singing had an effect on the characteristics of the speaking voice Voice Assessment in Rock Singers Folia Phoniatr Logop 2013;65:248–256 DOI: 10.1159/000357707 Methods Participants Twenty-one rock singers (19 men and women) participated as subjects in the present study (experimental group) Their average age was 26 years, with a range from 19 to 34 years All were native Spanish speakers and recruited from amateur rock bands Since one of the authors of the present study (A.H.) belongs to the singing rock field, he contacted and recruited the participants The inclusion criteria were: (1) experience producing growl voice and/ or reinforced falsetto for at least year, and (2) practice of the technique at least times a month during performances or rehearsals None of the participants reported previous voice therapy/training None of the participants had a hearing impairment All participants were asked to explain and produce the voice techniques they use in rock singing before undergoing endoscopic examination This procedure was perceptually verified by of the authors of the present study, all of whom were speech-language pathologists with experience in singing voice A control group was also included in the present study Eighteen pop singers (14 men and women) with more than years of experience performing different pop styles (except rock) were recruited for the same voice assessment Their average age was 28 years, with a range from 20 to 32 years The experiments were con- 249 ducted with the understanding and the written consent of each participant Participants from both experimental and control groups underwent an evaluation session lasting no more than h This session included (1) application of the Singing Voice Handicap Index (S-VHI), (2) voice recording, and (3) laryngoscopic evaluation Individual explanation and demonstrations were provided about the required tasks before performing the examinations Questionnaire Application All participants were asked to complete the Spanish adaptation and validation of the S-VHI This self-administrated questionnaire is a health status instrument designed to assess the voice handicap resulting from singing voice problems [21, 22] The S-VHI has important psychometric properties of reliability and validity It contains 36 items chosen to address the physical, emotional, social, and economic impact of singing voice problems Each item is individually scored on a 5-point Likert scale anchored by ‘never’ (score of 0) and ‘always’ (score of 4) Recording Procedure Subjects were required to produce three repetitions of a sustained vowel /a/ using a comfortable fundamental frequency and loudness level; each vowel was sustained for s The vowel productions were recorded in an acoustically treated booth, with an ambient noise level below 30 dB For the recording, a Focusrite Saffire USB interphase (Focusrite, Calif., USA) and an omnidirectional condenser microphone (Samson MM01, Samson Technologies Corp., Hauppauge, N.Y., USA) positioned at a distance of 20 cm from the mouth, with a 45° inclination angle was used Samples were digitally recorded using Steinberg Cubase LE4 (Steinberg, Germany) software in a WAV format at a sampling rate of 44.1 kHz with 16 bits/sample quantization Acoustic Analysis Acoustic analysis of all recorded sustained vowels included harmonic-to-noise ratio (HNR), frequency perturbation measure (jitter), and amplitude perturbation measure (shimmer) They were obtained by PRAAT software, version 5.0.23 (Bergsma & Weenink, 2008) Recorded samples were edited prior to acoustic analysis The first and last second of each sample were excluded, leaving the central s for analysis The editing procedure was carried out using Goldwave v5.58 software (GoldWave Inc., St John’s, Nfld., Canada) Laryngoscopic Assessment After voice recordings, participants underwent a laryngoscopic examination They were asked to sit upright in a comfortable chair Assessment of laryngeal activity was carried out with a flexible fiberoptic endoscope (Pentax VNL-1170K, KayPENTAX, Lincoln Park, N.J., USA) connected to a video camera and a light source Analog images were digitalized with a Pentax EPK-1000 (KayPENTAX) digital processor All examinations were performed without topical nasal anesthesia The laryngoscopic procedure was carried out by a laryngologist with more than 20 years of experience in singing and speaking voice assessment During singing voice tasks, the flexible endoscope was placed near the tip of the uvula, allowing a full view of the pharynx and larynx This placement was set by securing the fiberscope against the alar cartilage of the nose with the laryngologist’s finger A steady placement of the fiberscope is crucial since observation of laryngeal height adjustments and other laryngeal configurations can be af- 250 Folia Phoniatr Logop 2013;65:248–256 DOI: 10.1159/000357707 fected by movement of the endoscope During regular speaking endoscopic procedures, the flexible endoscope was placed right above the epilaryngeal tube For the purposes of this study, two main aspects were observed during the laryngoscopic procedure: (1) regular speaking voice laryngoscopic assessment (for both groups), and (2) assessment during production of growl voice and reinforced falsetto (only for the experimental group) Phonatory tasks during the first stage were: sustained vowels and running speech tasks To assess growl voice, subjects from the experimental group were asked to produce a sustained vowel /a/ using a comfortable fundamental frequency (middle range) and loudness level To evaluate reinforced falsetto, participants were required to produce a sustained vowel in the highest possible pitch using the most comfortable vowel and loudness level Recall that not all the participants produced both growl voice and reinforced falsetto This information was previously obtained during the recruitment process Possible laryngeal constrictions, vertical laryngeal position and pharyngeal activity were assessed during both growl voice and reinforced falsetto after laryngoscopic recording was made Visual Evaluation of Laryngoscopic Samples Two fellowship-trained laryngologists blinded to the purpose and nature of the study were asked to review the laryngoscopic examinations and rate the degree of A-P laryngeal compression, medial laryngeal compression, pharyngeal constriction, and vertical laryngeal position on a 5-point scale For vertical laryngeal position 1 = very low, 5 = very high, for medial laryngeal compression 1 = very opened, 5 = very narrow, for A-P laryngeal compression 1 = very opened, 5 = very narrow, and for pharyngeal width 1 = very wide, 5 = very narrow Moreover, raters were asked to evaluate the presence of masses, edema, erythema, glottal chink, and other possible laryngeal alterations (presence  = 1, absence  = 0) This visual assessment was performed for videos obtained from both experimental and control groups For the experimental group only, a similar visual evaluation was carried out to evaluate growl voice and reinforced falsetto The degree of medial and A-P laryngeal compression, medial laryngeal compression, pharyngeal constriction, and vertical laryngeal position was assessed on the same 5-point scale All sound was removed Each laryngoscopic examination could be reviewed as many times as desired Perceptual Evaluation Voice audio samples of sustained vowels from both experimental and control groups were perceptually assessed by external raters All three repetitions of the vowel (from each participant) were used for this part of the analysis This group of blinded judges consisted of speech-language pathologists with at least years of experience working with patients with voice disorders The order of recordings was randomized Perceptual assessment was performed with the GRBAS scale [23] The GRBAS scale evaluates five parameters: G = grade of dysphonia, R = roughness, B = breathiness, A = asthenic quality, and S = strain quality Perceptual variables were assessed using a 4-point scale (from to 3), where 0 = normal, 1 = slight, 2 = moderate, and 3 = severe Raters could replay each sample as many times as they wanted before making their determination and moving on to the next recording The evaluation was performed in a sound-treated room using a laptop computer and a high-quality Audioengine loudspeaker (Audioengine, Kowloon, Hong Kong) The listeners were located at approximately m from the loudspeaker All the listeners reported normal hearing Guzman/Barros/Espinoza/Herrera/Parra/ Muñoz/Lloyd Statistical Analysis Descriptive statistics were calculated for the variables, including mean and standard deviation A kappa test was performed to assess the interrater concordance for each auditory perceptual parameter and cut-off point of >0.60 was used Intraclass correlation coefficients were computed to assess intrarater concordance Moreover, a Spearman correlation analysis between acoustic parameters, S-VHI and perceptual assessment was performed; the correlational analysis only used the G (grade) dimension from the GRBAS scale The results and the comparisons between experimental and control groups were assessed using Wilcoxon’s rank-sum test for continuous variables, and χ2 test and Fisher’s exact for categorical variables A p value 0.60) No significant differences were found between groups for all laryngoscopic features Therefore, there are no structural or functional laryngeal differences when comparing rock and pop singers Of the 21 subjects from the experimental group, (33.3%) presented with normal laryngeal anatomy This includes normality of all laryngeal structures including the vocal folds The remaining participants demonstrated varying degrees of alteration in some laryngeal structures Eight of them presented with slight vocal fold erythema, and singers showed a slight degree of edema in the posterior laryngeal commissure (possibly due to laryngealpharyngeal reflux) Moreover, subjects presented with slight asymmetry of the false vocal folds and participants demonstrated excessive laryngeal mucous No mass lesions (polyps, nodules, cysts, edemas, etc.) were found in any participant Voice Assessment in Rock Singers Table Mean and standard deviation of acoustic analysis for ex- perimental and control groups Jitter Shimmer HNR Experimental Control p value 0.29±0.17 1.55±0.54 23.64±3.84 0.36±0.21 1.68±0.51 22.40±4.62 0.2989 0.4924 0.3874 Table Intra- and interrater reliability analysis for laryngoscopic assessment Masses Edema Erythema VLP MLC A-P LC Pharyngeal constriction Glottal chink Others Experimental group Control group interrater (kappa; p value) intrarater (ICC; p value) interrater (kappa; p value) intrarater (ICC; p value) – 0.57; 0.009 0.66; 0.007 0.70; 0.005 0.81; 0.0001 0.88;