Juha Vintturi

Objective Analysis of Vocal Warm-Up with Special Reference to Ergonomic Factors

Vocal warm-up was studied in terms of changes in voice parameters during a 45-minute vocal loading session in the morning. The voices of a randomly chosen group of 40 female and 40 male young students were loaded by having them read a novel aloud. The exposure groups (5 females and 5 males per cell) consisted of eight combinations of the following factors: (1) low (25 +/- 5%) or high (65 +/- 5%) relative humidity of ambient air; (2) low [< 65 dB(SPL)] or high [> 65 dB(SPL)] speech output level during vocal loading; (3) sitting or standing posture during vocal loading. Two sets of voice samples were recorded: a resting sample before the loading session and a loading sample after the loading session. The material recorded consisted of /pa:ppa/ words produced normally, as softly and as loudly as possible in this order by all subjects. The long /a/ vowel of the test word was inverse-filtered to obtain the glottal flow waveform. Time domain parameters of the glottal flow [open quotient (OQ), closing quotient (CQ), speed quotient (SQ), fundamental frequency (F0)], amplitude domain parameters of the glottal flow [glottal flow (fAC) and its logarithm, minimum of the first derivative of the glottal flow (dpeak) and its logarithm, amplitude quotient (AQ), and a new parameter, CQAQ], intraoral pressure (p), and sound pressure level (SPL) values of the phonations were analyzed. Voice range profiles (VRP) and the singers formant (g/G, a/A, cl/c, e1/e, g1/g for females/males) of the loud phonation were also measured. Statistically significant differences between the preloading and postloading samples could be seen in many parameters, but the differences depended on gender and the type of phonation. In females the values of CQ, AQ, and CQAQ decreased and the values of SQ and p increased in normal phonations; the values of fAC, dpeak, and SPL increased in soft phonations; the values of AQ and CQAQ decreased in loud phonations; the harmonic energy in the singers formant region increased significantly at every pitch. In males the values of OQ and AQ decreased and the values of dpeak, F0, p, and SPL increased in normal phonations; the values of fAC and p increased in soft phonations. The changes could be interpreted as signs of a shift toward hyperfunctional voice production. Low humidity was associated with more hyperfunctional changes than high humidity. High output was associated with more hyperfunctional changes than low output. Sitting position was associated with an increasing trend at both margins of male VRP, whereas the case was the opposite for standing position.

Loading-related subjective symptoms during a vocal loading test with special reference to gender and some ergonomic factors.

Vocal loading-related subjective symptoms were studied in a day-long vocal loading test. The voices of 40 female and 40 male voluntary young students were loaded by having them read aloud a novel for five times 45 min. The subjective symptoms that occurred during the vocal loading session were reported by filling in a questionnaire after each session. The responses loaded on five factors in a factor analysis: (1) ‘central fatigue’; (2) ‘symptoms of the neck, shoulders and back’; (3) ‘drying in the mouth and throat’; (4) ‘symptoms of the throat’; (5) ‘symptoms of the voice’. The exposure groups (5 females and 5 males per cell) consisted of eight combinations of the following factors: (1) low (25 ± 5%) or high (65 ± 5%) relative humidity of ambient air; (2) low [<65 dB(SPL)] or high [>65 dB(SPL)] speech output level of vocal loading; (3) sitting or standing posture during vocal loading. The lowest mean score for symptoms pooled over the test were found in ‘symptoms of the neck, shoulders and back’ and the highest mean symptom score in ‘drying in the mouth and throat’ and ‘symptoms of the throat’. Most symptoms were at their minimum during the first loading session and increased statistically significantly to a peak mean value after three or five vocal loading sessions. Statistically significant differences in the mean level between the gender or exposure groups emerged for ‘central fatigue’ (humidity had clear effects) and ‘symptoms of the neck, shoulders and back’ (gender, humidity and posture had clear effects). In these cases, females had more symptoms than males; the low-humidity group had more symptoms than the high-humidity group, and the standing subjects had more symptoms than the sitting subjects.

Measuring the effect of fundamental frequency raising as a strategy for increasing vocal intensity in soft, normal and loud phonation

A method is presented to estimate the effect of intentional raising of fundamental frequency (F0) on vocal intensity. The method, energy of the synthesised period (ESP), is based on computation of the energy of a hypothetical speech sound synthesised using a single period of the glottal volume velocity waveform and a digital filter that models the vocal tract. If the intensity of speech is regulated by modifying either the characteristics of glottal flow or the vocal tract, the change in the ESP-value should correspond to an equal change in the value of the sound pressure level (SPL). However, F0 can only change the value of SPL, but has no effect on ESP. Hence, by comparing the behaviours of SPL and ESP, it is possible to measure the way in which speakers use F0 raising as a strategy to increase vocal intensity. The results show that, in producing loud voice, speakers use F0 to increase the number of glottal closures per time unit, which increases rapid fluctuations in the speech pressure waveform, which, in turn, raises vocal intensity. The average increase of SPL due to this active use of F0 was approximately 4 dB in loud speech produced by both female and male speakers.

The Effects of Post-Loading Rest on Acoustic Parameters with Special Reference to Gender and Ergonomic Factors

It is a common experience that vocal quality changes during a break in vocal loading. The purpose of the present study was (1) to analyse the effects of a short post-loading vocal rest in terms of changes in a large variety of voice parameters and (2) to assess the possible effects of gender and exposure factors on these changes. The voices of a randomly chosen group of 40 female and 40 male young students were loaded by having them read aloud a novel. Two sets of voice samples were recorded: a post-loading sample after three times 45-min vocal loading during the morning and a post-resting sample after a 45-min lunch break. The material recorded consisted of /pa:ppa/ words produced normally, as softly and as loudly as possible in this order. The long /a/ vowel of the test word was inverse-filtered to obtain the glottal flow waveform. Time-domain parameters of the glottal flow [open quotient, closing quotient (ClQ), speed quotient (SQ), fundamental frequency (F₀)], amplitude-domain parameters of the glottal flow [glottal flow, minimum of the first derivative of glottal flow, amplitude quotient (AQ)], intraoral pressure and sound pressure level (SPL) values of the phonations were analysed. Voice range profiles and the singer’s formant (g/G, a/A, c∣/c, e∣/e, g∣/g for females/males) of the loud phonations were also measured. The subjects were divided into eight exposure groups (5 females and 5 males per cell) according to different combinations of the following exposure factors: (1) low (25 ± 5%) or high (65 ± 5%) relative humidity of ambient air, (2) low [<65 dB(A)] or high [>65 dB(A)] speech output level during vocal loading and (3) sitting or standing posture during vocal loading. Statistically significant differences between the post-loading and post-resting samples could be observed in many parameters (the values of intraoral pressure in the soft phonations decreased, the values of SPL and SQ in the normal phonations decreased and the values of AQ, F₀ and ClQ in the normal phonations increased). Most of the differences reflected a shift towards softer phonation. Gender and exposure factors also had significant effects.

Dynamic Extremes of Voice in the Light of Time Domain Parameters Extracted from the Amplitude Features of Glottal Flow and Its Derivative

In the first part of the study, the subjects (4 females, 4 males) produced sustained breathy, normal and pressed types of phonation. The maximum AC flow (fac) and the negative peak amplitude (dmin) of the first derivative of the glottal flow were extracted from glottal volume velocity waveforms estimated by inverse filtering. The ratio between fac and dmin (amplitude quotient, AQ), which gives an estimate of the closing time of the glottal flow, and its normalised version (NAQ) were computed. The NAQ values correlated strongly with the closing quotient of glottal flow. In the second part of the study, the aim was to investigate the dynamic extremes of the human voice in terms of F₀, SPL, fac, dmin, AQ and NAQ as well as the intraoral pressure (p) used for subglottal pressure estimation. Eleven normal subjects (5 females, 6 males) participated in this experiment. The subjects started with the production of soft phonation (approximately 55 dB at 40 cm) and increased their vocal intensity at 5-dB steps up to the level of 105 dB. At the analysis stage, the voice samples were divided into three categories: soft (<70 dB), normal (70–90 dB) and loud (>90 dB). In soft and normal phonation, intensity change was correlated with changes in the shape of the glottal flow waveform, whereas the loud voice samples showed a large increase in F₀ and p values. At the loudest extreme, dmin approached its maximum and AQ its minimum values and NAQ started to rise. In terms of the NAQ values of stressed syllables, the type of phonation was breathy in the soft intensity category, whereas in the normal and loud intensity categories it was within the range of the pressed type of phonation of sustained phonation samples.

Laryngeal fractures: clinical findings and considerations on suboptimal outcome.

Conclusion. We recommend early surgical exploration and fixation for patients with dislocated or comminuted laryngeal fractures to avoid long-term voice complications. One-third of 33 fracture patients rated their voice after the fracture had healed as fair but altered. Objectives. To examine the indications for and the outcome of surgical management in patients with laryngeal fractures. Patients and methods. The study was carried out in a tertiary care referral university hospital and was a retrospective study of case series. Thirty-three consecutive patients, aged 14–84 years, presented with various types of laryngeal fractures. Patients were staged according to the type of the fracture and surgical correction was performed when indicated. Voice outcome was documented and patients with subjectively suboptimal result were further evaluated by phoniatric specialist. Results. In all, 32 of 33 laryngeal fracture patients had blunt trauma and the main causative factors were sport injuries (39%) and physical assault (33%). All of the 33 laryngeal fracture patients had a good airway outcome. The subjective voice outcome was good for 20 (61%) and fair for 13 (39%) patients. The mean follow-up time was 39.5 months (range 2–114 months). In phoniatric evaluation most (six of eight) patients with fair voice outcome could not produce high pitched voices because of inability to stretch the vocal folds.

On the linearity of the relationship between the sound pressure level and the negative peak amplitude of the differentiated glottal flow in vowel production

The negative peak amplitude of the differentiated glottal flow (dpeak) is known to correlate strongly with the sound pressure level (SPL) of speech. Therefore, the function between dpeak and SPL has been conventionally modeled as a single line. In this survey, the linearity of the function between dpeak and SPL is revisited by analyzing glottal flows that were inverse filtered from speech sounds of largely different intensities. It is shown that SPL–dpeak-graphs can be modeled more accurately by using two linear functions, the first of which models soft phonation, and the second of which models normal and loud speech sounds. For all of the analyzed SPL–dpeak-graphs, the slope of the modeling line matching soft phonation was larger than the slope of the line for normal and loud speech. This result suggests that vocal intensity is affected not only by the single amplitude domain value of the voice source, dpeak, but also by the shape of the differentiated glottal flow near the instant of the negative peak.

Evidence of the significance of secondary excitations of the vocal tract for vocal intensity.

In the production of voiced speech the main excitation of the vocal tract occurs during the glottal closing phase when the rate of change of the flow reaches its absolute maximum. The level of this maximum, the negative peak amplitude of the differentiated glottal flow, correlates strongly with sound pressure level. This study presents a straightforward method that yields a numerical value to characterize the effect of the main excitation on vocal intensity. The method, energy ratio by modified excitation (ERME), utilizes the glottal flow and the vocal tract transfer function estimated by inverse filtering and it synthesizes two signals based on the linear source-filter theory. The first sound is produced using the glottal flow given by inverse filtering per se. The second signal is synthesized by removing the main excitation from the differentiated flow. ERME is defined as the ratio between the energy of the first synthesized signal and the energy of the second one. It is shown that when the loudness of speech increases, the value of ERME first rises but in the case of very loud voices it starts to decrease. Hence, ERME shows that effects of secondary excitations of the vocal tract that occur during glottal opening become important in the production of very loud voices.