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| 2. |
- Sun, Zhongxi, et al.
(författare)
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Degradation kinetics of ethyl-xanthate as a function of pH in aqueous solution
- 1997
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Ingår i: Minerals Engineering. - 0892-6875 .- 1872-9444. ; 10:4, s. 389-400
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Tidskriftsartikel (refereegranskat)abstract
- Xanthate degradation kinetics plays an important role in sulfide mineral flotation and in the treatment of flotation tailings. Increasing environmental concern about consequences of flotation tailings makes this information even more important. In this paper, the degradation kinetics of xanthate in homogeneous solution as a function of pH at 5 °C, 20 °C and 40 °C is systematically studied by UV-Visible spectrophotometric measurements. The results indicate that the degradation of ethyl xanthate is rapidly increased with decreasing pH at pH<7. At pH 7-8, the maximum half-life of the xanthate appears. The degradation was faster at pH 9-10, but at pHgt;10 the half-lives of xanthate once again increase. The investigations are also extended to different media other than pure water, such as, 0.1 M NaClO4, 0.1 M NaNO3 0.1 M NaCl as well as in the supernatants of flotation tailings of sulfide minerals.The rate constants of xanthate degradation are calculated and presented together with half-lives and activation energies of xanthate degradation. The degradation products and reaction mechanisms are discussed based on experimental results.
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| 9. |
- Evertsson, Magnus, 1967, et al.
(författare)
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Investigation of Interparticle Breakage as Applied to Cone Crushing
- 1997
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Ingår i: Minerals Engineering. - 0892-6875. ; 10, s. 199-214
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Tidskriftsartikel (refereegranskat)abstract
- The breakage of material in cone type gyratory crushers is traditionally regarded as relying upon single particle breakage. In the last ten years the emphasis has shifted with manufacturers trying to generate higher degrees of interparticle breakage. Increasing the degree of interparticle crushing is claimed to improve crushing efficiency and product shape. The current study uses form conditioned crushing tests (geometry controlled compression) to investigate how multiple particles respond to crushing loads. By variation of test parameters the breakage characteristics of a rock material can be determined and compared to traditional single particle crushing. The selection function, S (probability of crushing a single particle), seems to be related to the ratio between stroke and bed height, s/b, with a second order polynomial in s/b. An analysis of a given crusher chamber gives selection values in the range 0.05
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| 25. |
- Saunders, Carol D., et al.
(författare)
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Summative Evaluation of "The Swamp": : A Conservation Exhibit with a Big Idea
- 1997
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Ingår i: Visitor Behavior. - Jacksonville, FL, USA. - 0892-4996. ; XII:1 & 2, s. 4-7
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Tidskriftsartikel (refereegranskat)abstract
- In this article, Carol D. Saunders and H. Elizabeth Stuart Perry of the Brookfield Zoo provide findings from the summative evaluation of "The Swamp." This immersive wetlands exhibit was designed to encourage people to appreciate the benefits of ecosystems and features animals and plants of a cypress swamp and of an Illinois riverine wetland.
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| 33. |
- McAllister, Anita, et al.
(författare)
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Perturbation and hoarseness : a pilot study of six children's voices.
- 1996
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Fundamental frequency (FO) perturbation has been found to be useful as an acoustic correlate of the perception of dysphonia in adult voices. In a previous investigation, we showed that hoarseness in children's voices is a stable concept composed mainly of three predictors: hyperfunction, breathiness, and roughness. In the present investigation, the relation between FO perturbation and hoarseness as well as its predictors was analyzed in running speech of six children representing different degrees of hoarseness. Two perturbation measures were used: the standard deviation of the distribution of perturbation data and the mean of the absolute value of perturbation. The results revealed no clear relation.
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| 34. |
- Ternström, Sten, 1956-
(författare)
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Hearing myself with others : sound levels in choral performance measured with separation of one's own voice from the rest of the choir.
- 1994
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 8:4, s. 293-302
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Tidskriftsartikel (refereegranskat)abstract
- The choir singer has two acoustic signals to attend to: the sound of his or her own voice (feedback), and the sound of the rest of the choir (reference). The balance in loudness between feedback and reference is governed mainly by the room acoustics. Although earlier experiments have shown that singers have a fairly large tolerance for imbalance, with references ranging from -23 to +5 dB, experience suggests that, when singers are given control over this parameter, their preferences are much narrower. A quantification of the optimum balance would be useful in the design of concert stages and rehearsal halls. A method is described for measuring the feedback and reference levels as experienced by singers under live performance conditions. Recordings were made using binaural microphones worn by choir singer subjects. With the given combination of choir and room, it was possible to achieve adequate separation of the feedback and reference signals with simple signal processing. The feedback-to-reference ratio averaged over the 12 singers was found to be +3.9 dB, with extremes of +1.5 and +7.3 dB.
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| 35. |
- Ternström, Sten, 1956-
(författare)
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Perceptual evaluations of voice scatter in unison choir sounds.
- 1993
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 7:2, s. 129-135
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Tidskriftsartikel (refereegranskat)abstract
- The preferences of experiences listerners for pitch and formant frequency dispersion in unison choir sounds were explored using synthesized stimuli. Two types of dispersion were investigated: (a) pitch scatter, which arises when voices in an ensemble exhibit small differences in mean fundamental frequency, and (b) spectral smear, defined as such dispersion of formants 3 to 5 as arises from differences in vocal tract length. Each stimulus represented a choir section of five bass, tenor, alto, or soprano voices, producing the vowel [u], [a], or [ae]. Subjects chose one dispersion level out of six available, selecting the "maximum tolerable" in a first run and the "preferred" in a second run. The listeners were very different in their tolerance for dispersion. Typical scatter choices were 14 cent standard deviation for "tolerable" and 0 or 5 cent for "preferred." The smear choices were less consistent; the standard deviations were 12 and 7%, respectively. In all modes of assessment, the largest dispersion was chosen for the vowel [u] on a bass tone. There was a vowel effect on the smear choices. The effects of voice category were not significant.
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| 36. |
- Gramming, Patricia, et al.
(författare)
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Relationship between changes in voice pitch and loudness
- 1988
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 2:2, s. 118-126
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Tidskriftsartikel (refereegranskat)abstract
- Summary Changes in mean fundamental frequency accompanying changes in loudness of phonation are analyzed in 9 professional singers, 9 nonsingers, and 10 male and 10 female patients suffering from vocal functional dysfunction. The subjects read discursive texts with noise in earphones, and some also at voluntarily varied vocal loudness. The healthy subjects phonated as softly and as loudly as possible at various fundamental frequencies throughout their pitch ranges, and the resulting mean phonetograms are compared. Mean pitch was found to increase by about half-semitones per decibel sound level. Grossly, the subject groups gave similar results, although the singers changed voice pitch more than the nonsingers. The voice pitch changes may be explained as passive results of changes of subglottal pressure required for the sound level variation.
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| 37. |
- Granqvist, Svante, 1963-, et al.
(författare)
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Simultaneous analysis of vocal fold vibration and transglottal airflow : exploring a new experimental setup
- 2003
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 17, s. 319-330
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Tidskriftsartikel (refereegranskat)abstract
- Summary: The purpose of this study was to develop an analysis system for studying the relationship between vocal fold vibration and the associated transglottal airflow. Recordings of airflow, electroglottography (EGG), oral air pressure, and acoustic signals were performed simultaneously with high-speed imaging at a rate of approximately 1900 frames/s. Inverse filtered airflow is compared with the simultaneous glottal area extracted from the high-speed image sequence. The accuracy of the synchronization between the camera images and the foot pedal synchronization pulse was examined, showing that potential synchronization errors increase with time distance to the synchronization pulse. Therefore, analysis was limited to material near the synchronization pulse. Results corroborate previous predictions that air flow lags behind area, but also they reveal that relationships between these two entities may be complex and apparently varying with phonation mode.
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| 38. |
- Lindestad, Per Å, et al.
(författare)
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Voice source characteristics in mongolian throat singing studied with high-speed imaging technique, acoustic spectra, and inverse filtering
- 2001
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 15:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- Mongolian “throat singing” can be performed in different modes. In Mongolia, the bass-type is called Kargyraa. The voice source in bass-type throat singing was studied in one male singer. The subject alternated between modal voice and the throat singing mode. Vocal fold vibrations were observed with high-speed photography, using a computerized recording system. The spectral characteristics of the sound signal were analyzed. Kymographic image data were compared to the sound signal and flow inverse filtering data from the same singer were obtained on a separate occasion. It was found that the vocal folds vibrated at the same frequency throughout both modes of singing. During throat singing the ventricular folds vibrated with complete but short closures at half the frequency of the true vocal folds, covering every second vocal fold closure. Kymographic data confirmed the findings. The spectrum contained added subharmonics compared to modal voice. In the inverse filtered signal the amplitude of every second airflow pulse was considerably lowered. The ventricular folds appeared to modulate the sound by reducing the glottal flow of every other vocal fold vibratory cycle.
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| 39. |
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| 40. |
- Södersten, M., et al.
(författare)
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Vocal behavior and vocal loading factors for preschool teachers at work studied with binaural DAT recordings
- 2002
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Ingår i: Journal of Voice. - : Mosby. - 0892-1997 .- 1873-4588. ; 16:3, s. 356-371
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Tidskriftsartikel (refereegranskat)abstract
- Preschool teachers are at risk for developing voice problems such as vocal fatigue and vocal nodules. The purpose of this report was to study preschool teachers' voice use during work. Ten healthy female preschool teachers working at daycare centers (DCC) served as subjects. A binaural recording technique was used. Two microphones were placed on both sides of the subject's head, at equal distance from the mouth, and a portable DAT recorder was attached to the subject's waist. Recordings were made of a standard reading passage before work (baseline) and of spontaneous speech during work. The recording technique allowed separate analyses of the level of the background noise, and of the subjects' voice sound pressure level, mean fundamental frequency, and total phonation time. Among the results, mean background noise level for the ten DCCs was 76.1 dBA (range 73.0-78.2), which is more than 20 dB higher than what is recommended where speech communication is important (50-55 dBA). The subjects spoke on an average of 9.1 dB louder (p < 0.0001), and with higher mean fundamental frequency (247 Hz) during work as compared to the baseline (202 Hz) (p < 0.0001). Mean phonation time for the group was 17%, which was considered high. It was concluded that preschool teachers do have a highly vocally demanding profession. Important steps to reduce the vocal loading for this occupation would be to decrease the background noise levels and include pauses so that preschool teachers can rest their voices.
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| 41. |
- Ternström, Sten, et al.
(författare)
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Cancellation of simulated environmental noise as a tool for measuring vocal performance during noise exposure
- 2002
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Ingår i: Journal of Voice. - 0892-1997 .- 1873-4588. ; 16:2, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- It can be difficult for the voice clinician to observe or measure how a patient uses his voice in a noisy environment. We consider here a novel method for obtaining this information in the laboratory. Worksite noise and filtered white noise were reproduced over high-fidelity loudspeakers. In this noise, I I subjects read an instructional text of 1.5 to 2 minutes duration, as if addressing a group of people. Using channel estimation techniques, the site noise was suppressed from the recording, and the voice signal alone was recovered. The attainable noise rejection is limited only by the precision of the experimental setup, which includes the need for the subject to remain still so as not to perturb the estimated acoustic channel. This feasibility study, with 7 female and 4 male subjects, showed that small displacements of the speaker's body, even breathing, impose a practical limit on the attainable noise rejection. The noise rejection was typically 30 dB and maximally 40 dB down over the entire voice spectrum. Recordings thus processed were clean enough to permit voice analysis with the long-time average spectrum and the computerized phonetogram. The effects of site noise on voice sound pressure level, fundamental frequency, long-term average spectrum centroid, phonetogram area, and phonation time were much as expected, but with some interesting differences between females and males.
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| 42. |
- Ternström, Sten, 1956-
(författare)
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Physical and acoustic factors that interact with the singer to produce the choral sound
- 1991
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Ingår i: Journal of Voice. - : Elsevier. - 0892-1997 .- 1873-4588. ; 5:2, s. 128-143
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Tidskriftsartikel (refereegranskat)abstract
- Most of the people who perform music do so in the capacity of choir singers. An understanding of the particular acoustic properties of the choral sound is of interest not only to performers, but also to educators, architectural acousticians, audio technicians, and composers. The goal of choir acoustics is to describe various aspects of choral sound in acoustic terms, thereby taking into account the acoustics of voice production, the acoustics of rooms, and psychoacoustic properties of the auditory system. This article is an overview of choir acoustics research done in Stockholm over the past 8 years. It is an abridged and adapted version of an overview given in the author’s dissertation, Acoustical Aspects of Choir Singing. Three different kinds of experiments were made: (a) the control of phonation frequency and the vowel articulation of choir singers were investigated, by having individual choir singers perform vocal tasks on demand or in response to auditory stimuli; (b) typical values of sound levels, phonation frequency scatter, and long-time averaged spectra were obtained by measurements on choir singers rehearsing in ensemble under normal or near-normal conditions; and (c) models for certain aspects of choral sound were formulated and evaluated by synthesis. The choir singer’s performance is based on two acoustic signals: her or his own voice (the feedback) and the rest of the choir (the reference). Intonation errors were found to be induced or increased by (a) large level differences between the feedback and the reference, (b) several perceptually unfavorable spectral properties of the reference, and (c) articulatory maneuvers, i.e., intrinsic pitch. The magnitude of the errors would be indirectly related to room acoustics (a and b) and to voice usage and musical/textual content (b and c). When singing alone, singers from one choir used a vowel articulation that was different from that in speech and also more unified; it was also in some respects different from solo singing. Long-time average spectrum effects of room acoustics and musical dynamics were large, as expected; those of choir type and musical material were smaller. To some extent, choirs adapted their sound level and voice usage to the room acoustics. Small random fluctuations in phonation frequency, called "€œflutter"€ and "€œwow,"€ are always present in human voices. With multiple voices, flutter and wow cause, through interference, a pseudorandom, independent amplitude modulation of partial tones, which is known to cue the perceptual "€œchorus effect." The chorus effect is also influenced by the reverberation properties of the room. Choral sounds were explored by means of synthesis, and the importance of realistic flutter was established. Flutter in choir singers was analyzed and simulated in single synthesized voices. Expert listeners were unable to discriminate between simulated and authentic flutter.
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| 43. |
- White, Peta, 1961-
(författare)
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Formant frequency analysis of children's spoken and sung vowels using sweeping fundamental frequency production
- 1999
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Ingår i: Journal of Voice. - : Singular Publishing Group. - 0892-1997 .- 1873-4588. ; 13:4, s. 570-582
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Tidskriftsartikel (refereegranskat)abstract
- High-pitched productions present difficulties in formant frequency analysis due to wide harmonic spacing and poorly defined formants. As a consequence, there is little reliable data regarding children's spoken or sung vowel formants. Twenty-nine 11-year-old Swedish children were asked to produce 4 sustained spoken and sung vowels. In order to circumvent the problem of wide harmonic spacing, F-1 and F-2 measurements were taken from vowels produced with a sweeping F-0. Experienced choir singers were selected as subjects in order to minimize the larynx height adjustments associated with pitch variation in less skilled subjects. Results showed significantly higher formant frequencies for speech than for singing. Formants were consistently higher in girls than in boys suggesting longer vocal tracts in these preadolescent bays. Furthermore, formant scaling demonstrated vowel dependent differences between boys and girls suggesting non-uniform differences in male and female vocal tract dimensions. These vowel-dependent sex differences were not consistent with adult data.
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| 44. |
- Andrade, Pedro Amarante, et al.
(författare)
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The Flow and Pressure Relationships in Different Tubes Commonly Used for Semi-occluded Vocal Tract Exercises
- 2016
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Ingår i: Journal of Voice. - : Mosby-Elsevier. - 0892-1997 .- 1873-4588. ; 30:1, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- This experimental study investigated the back pressure (Pback) versus flow (U) relationship for 10 different tubes commonly used for semi-occluded vocal tract exercises, that is, eight straws of different lengths and diameters, a resonance tube, and a silicone tube similar to a Lax Vox tube. All tubes were assessed with the free end in air. The resonance tube and silicone tube were further assessed with the free end under water at the depths from 1 to 7 cm in steps of 1 cm. The results showed that relative changes in the diameter of straws affect Pback considerably more compared with the same amount of relative change in length. Additionally, once tubes are submerged into water, Pback needs to overcome the pressure generated by the water depth before flow can start. Under this condition, only a small increase in Pback was observed as the flow was increased. Therefore, the wider tubes submerged into water produced an almost constant Pback determined by the water depth, whereas the thinner straws in air produced relatively large changes to Pback as flow was changed. These differences may be taken advantage of when customizing exercises for different users and diagnoses and optimizing the therapy outcome.
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| 47. |
- Baker, C. P., et al.
(författare)
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CPPS and Voice-Source Parameters : Objective Analysis of the Singing Voice
- 2024
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Ingår i: Journal of Voice. - : Elsevier BV. - 0892-1997 .- 1873-4588. ; 38:3, s. 549-560
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: In recent years cepstral analysis and specific cepstrum-based measures such as smoothed cepstral peak prominence (CPPS) has become increasingly researched and utilized in attempts to determine the extent of overall dysphonia in voice signals. Yet, few studies have extensively examined how specific voice-source parameters affect CPPS values. Objective: Using a range of synthesized tones, this exploratory study sought to systematically analyze the effect of fundamental frequency (fo), vibrato extent, source-spectrum tilt, and the amplitude of the voice-source fundamental on CPPS values. Materials and Methods: A series of scales were synthesised using the freeware Madde. Fundamental frequency, vibrato extent, source-spectrum tilt, and the amplitude of the voice-source fundamental were systematically and independently varied. The tones were analysed in PRAAT, and statistical analyses were conducted in SPSS. Results: CPPS was significantly affected by both fo and source-spectrum tilt, independently. A nonlinear association was seen between vibrato extent and CPPS, where CPPS values increased from 0 to 0.6 semitones (ST), then rapidly decreased approaching 1.0 ST. No relationship was seen between the amplitude of the voice-source fundamental and CPPS. Conclusion: The large effect of fo should be taken into account when analyzing the voice, particularly in singing-voice research, when comparing pre and posttreatment data, and when comparing inter-subject CPPS data.
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| 48. |
- Baptista La, Filipa Martins, et al.
(författare)
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Pregnancy and the Singing Voice : Reports From a Case Study
- 2012
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Ingår i: Journal of Voice. - : Elsevier BV. - 0892-1997 .- 1873-4588. ; 26:4, s. 431-439
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. Significant changes in body tissues occur during pregnancy; however, literature concerning the effects of pregnancy on the voice is sparse, especially concerning the professional classically trained voice. Hypotheses. Hormonal variations and associated bodily changes during pregnancy affect phonatory conditions, such as vocal fold motility and glottal adduction. Design. Longitudinal case study with a semiprofessional classically trained singer. Methods. Audio, electrolaryngograph, oral pressure, and air flow signals were recorded once a week during the last 12 weeks of pregnancy, 48 hours after birth and during the following consecutive 11 weeks. Vocal tasks included diminuendo sequences of the syllable /pae/sung at various pitches, and performing a Lied. Phonation threshold pressures (PTPs) and collision threshold pressures (CTPs), normalized amplitude quotient (NAQ), alpha ratio, and the dominance of the voice source fundamental were determined. Concentrations of sex female steroid hormones were measured on three occasions. A listening test of timbral brightness and vocal fatigue was carried out. Results. Results demonstrated significantly elevated concentrations of estrogen and progesterone during pregnancy, which were considerably reduced after birth. During pregnancy, CTPs and PTPs were high; and NAQ, alpha ratio, and dominance of the voice source fundamental suggested elevated glottal adduction. In addition, a perceptible decrease of vocal brightness was noted. Conclusions. The elevated CTPs and PTPs during pregnancy suggest reduced vocal fold motility and increased glottal adduction. These changes are compatible with expected effects of elevated concentrations of estrogen and progesterone on tissue viscosity and water retention.
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| 49. |
- Beka, Ervin, et al.
(författare)
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Voice Changes Without Laryngeal Nerve Alterations After Thyroidectomy: The Need For Prospective Trials - A Review Study
- 2024
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Ingår i: Journal of Voice. - : MOSBY-ELSEVIER. - 0892-1997 .- 1873-4588. ; 38:1, s. 231-238
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Forskningsöversikt (refereegranskat)abstract
- Background. Thyroidectomy is a commonly performed surgical procedure that is offered for different thyroid pathologies. The most frequent complication after total thyroidectomy is transient or permanent hypoparathyroidism followed by transient or permanent recurrent laryngeal nerve palsy. Patients may experience voice impairment despite intact laryngeal nerve function. These patients are of special interest because they experience subjective symptoms which are difficult to measure and therefore to treat. Summary. The Voice Handicap Index (VHI) and VHI-10 are the most commonly used subjective questionnaires. Their results correlate with objective findings. Female sex, in particular after menopause, is a dominant factor for developing voice impairment after thyroidectomy. The extent of neck surgery and the weight and volume of the removed thyroid correlates directly with both objective and subjective voice impairment after surgery. Videolaryngostroboscopy should be considered to examine vocal cord pathologies in this patient group. Surprisingly, there are no studies showing that speech and voice therapy are beneficial for patients with voice alterations but with intact laryngeal nerves. Conclusions. While recurrent laryngeal nerve (RLN) paralysis can be evaluated by objective exams postoperatively, we are still left with the issue of possible partial or complete external branch of superior laryngeal nerve (EBSLN) injury. It is therefore quite difficult to segregate neural (RLN and EBSLN) and non -neural voice change populations, regardless of the method of literature evaluation. Perhaps patients' perspectives on how they experience voice functionality should play a superior role in deciding which patients should be investigated further with laryngoscopy, acoustic or perceptual analysis, and which patients should be offered treatment.
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