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Enflo, Laura
Publications (7 of 7) Show all publications
Enflo, L., Herbst, C. T., Sundberg, J. & McAllister, A. (2016). Comparing vocal fold contact criteria derived from audio and electroglottographic signals. Journal of Voice, 30(4), 381-388
Open this publication in new window or tab >>Comparing vocal fold contact criteria derived from audio and electroglottographic signals
2016 (English)In: Journal of Voice, ISSN 0892-1997, E-ISSN 1873-4588, Vol. 30, no 4, p. 381-388Article in journal (Refereed) Published
Abstract [en]

Collision threshold pressure (CTP), i.e., the lowest subglottal pressure producing vocal fold contact during phonation, is a parameter likely to reflect relevant vocal fold properties. The amplitude of an electroglottographic (EGG) signal or the amplitude of its first derivative (dEGG) has been used as the criterion of such contact. Manual measurement of CTP is time-consuming, making the development of a simpler, alternative method desirable. In this investigation we compare CTP values automatically derived from the dEGG signal to values measured manually, and to values derived from a set of alternative parameters, some obtained from audio and some from EGG signals. One of the parameters was the novel EGG wavegram, which visualizes sequences of EGG or dEGG cycles, normalized with respect to period and amplitude. Raters with and without previous acquaintance with EGG analysis marked the disappearance of vocal fold contact in dEGG and in wavegram displays of /pa:/-sequences produced with continuously decreasing vocal loudness by seven singer subjects. Vocal fold contact was equally accurately identified in displays of dEGG amplitude as of wavegram. Automatically derived CTP values showed high correlation with those measured manually, and with those derived from the ratings of the visual displays. Seven other parameters were tested as criteria of such contact. Mainly due to noise in the EGG signal, most of them yielded CTP values differing considerably from those derived from the manual and the automatic methods, while the EGG spectrum slope showed a high correlation. The possibility of measuring CTP automatically seems promising for future investigations.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Collision threshold pressure, vocal fold contact, wavegram, alpha, signal-to-noise ratio, EGG derivative, EGG spectrum slope, relative contact rise time, normalized amplitude quotient, relative dEGG amplitude
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-91364 (URN)10.1016/j.jvoice.2015.05.015 (DOI)000379526100001 ()
Note

Funding agencies:This research has been partially supported by the European Social Fund Project CZ.1.07/2.3.00/30.0004 "POST-UP" (C.T.H.).

Vid tiden för disputation förelåg publikationen som manuskript

Available from: 2013-04-23 Created: 2013-04-23 Last updated: 2017-05-02Bibliographically approved
Enflo, L., Sundberg, J. & McAllister, A. (2013). Collision and phonation threshold pressures before and after loud, prolonged vocalization in trained and untrained voices. Journal of Voice, 27(5), 527-530
Open this publication in new window or tab >>Collision and phonation threshold pressures before and after loud, prolonged vocalization in trained and untrained voices
2013 (English)In: Journal of Voice, ISSN 0892-1997, E-ISSN 1873-4588, Vol. 27, no 5, p. 527-530Article in journal (Refereed) Published
Abstract [en]

The phonation threshold pressure (PTP) is defined as the lowest subglottal pressure needed for obtaining and sustaining vocal fold oscillation. It has been found to increase during vocal fatigue. In the present study, PTP is measured together with the threshold pressure needed for vocal fold collision; henceforth, the collision threshold pressure (CTP). PTP and CTP are compared before and after loud, prolonged vocalization in singer and nonsinger voices. Ten subjects repeated the vowel sequence /a, e, i, o, u/ at a Sound Pressure Level of at least 80 dB at 0.3 m for 20 minutes. Audio and electroglottography signals were recorded before and after this exercise. At the same time, oral pressure was registered while the subjects produced a diminuendo repeating the syllable /pa:/, thus acquiring an approximate of the subglottal pressure. CTP and PTP increased significantly after the vocal loading in the nonsinger subjects. On the other hand, singers reported no substantial effect of the exercise, and most singers had a mean after-to-before ratio close to 1 for both CTP and PTP.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Collision threshold pressure, phonation threshold pressure, electroglottography, vocal fatigue, vocal loading, prolonged vocalization, singing training, vocal training
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-91359 (URN)10.1016/j.jvoice.2013.03.008 (DOI)000324249700001 ()
Available from: 2013-04-23 Created: 2013-04-23 Last updated: 2017-12-06Bibliographically approved
Enflo, L. (2013). Collision Threshold Pressure: A novel measure of voice function Effects of vocal warm-up, vocal loading and resonance tube phonation in water. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Collision Threshold Pressure: A novel measure of voice function Effects of vocal warm-up, vocal loading and resonance tube phonation in water
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The phonation threshold pressure (PTP), i.e., the smallest amount of subglottal pressure needed to initiate and sustain vocal fold oscillation, is frequently difficult to measure due to the difficulty for some subjects to produce extremely soft phonation. In addition, PTP values are often quite scattered. Hence, the collision threshold pressure (CTP), i.e., the smallest amount of subglottal pressure needed for vocal fold collision, was explored as a possible complement or alternative to PTP. Effects on CTP and PTP of vocal warm-up (Paper 1), resonance tube phonation with the tube end in water (Paper 2), and vocal loading (Paper 3) were investigated. With the aim to accelerate the CTP measurement process, comparisons were made between CTP values derived manually and those derived by several automatic or semi-automatic parameters (Paper 4).

Subjects were recorded at various F0 while phonating /pa:/-sequences, starting at medium loudness and continuing until phonation ceased. Subglottal pressure was estimated from oral pressure signals during the /p/ occlusion. Vocal fold contact was determined manually from the amplitude of the electroglottographic (EGG) signal (Papers 1 and 3) or its first derivative (dEGG) (Papers 2 and 4).

Recordings were made before and after exercise: (Paper 1) Vocal warm-up was carried out in the 13 singers’ own habitual way. (Paper 2) Twelve mezzo-sopranos phonated on /u:/ at various pitches for two minutes before post-recording, and 15 seconds before each additional F0, into a glass tube (l=27 cm, id=9 mm) at a water depth of 1-2 cm.

(Paper 3) Five trained singers and five untrained subjects repeated the vowel sequence /a,e,i,o,u/ at a Sound Pressure Level of at least 80 dB at 0.3 m for 20 minutes.

Statistically significant results: (Paper 1) CTP and PTP decreased after warm-up in the five female voices. CTP was found to be higher than PTP (about 4 H2O). Also, CTP had a lower coefficient of variation, suggesting that CTP is a more reliable measure than PTP. (Paper 2) CTP increased on average six percent after resonance tube phonation in water.

(Paper 3) CTP and PTP increased after the vocal loading in the untrained voices, with an average after-to-before ratio of 1.26 for CTP and 1.33 for PTP.

(Paper 4) Automatically derived CTP values showed high correlation with those obtained manually, from EGG spectrum slope, and from the visual displays of dEGG and of dEGG wavegram.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. p. 40
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1322
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-91365 (URN)978-91-7519-815-6 (ISBN)
Public defence
2013-05-24, Eken, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2013-04-23 Created: 2013-04-23 Last updated: 2019-12-08Bibliographically approved
Enflo, L., Sundberg, J., Romedahl, C. & McAllister, A. (2013). Effects on vocal fold collision and phonation threshold pressure of resonance tube phonation with tube end in water. Journal of Speech, Language and Hearing Research, 56, 1530-1538
Open this publication in new window or tab >>Effects on vocal fold collision and phonation threshold pressure of resonance tube phonation with tube end in water
2013 (English)In: Journal of Speech, Language and Hearing Research, ISSN 1092-4388, E-ISSN 1558-9102, Vol. 56, p. 1530-1538Article in journal (Refereed) Published
Abstract [en]

Purpose: Resonance tube phonation in water (RTPW) or in air is a voice therapy method successfully used for treatment of several voice pathologies. Its effect on the voice has not been thoroughly studied. This investigation analyzes the effects of RTPW on collision and phonation threshold pressures (CTP and PTP), the lowest subglottal pressure needed for vocal fold collision and phonation, respectively.

Method: Twelve mezzo-sopranos phonated into a glass tube, the end of which was placed under the water surface in a jar. Subglottal pressure, electroglottography and audio signals were recorded before and after exercise. Also, the perceptual effects were assessed in a listening test with an expert panel which also rated the subjects’ singing experience.

Results: Resonance tube phonation significantly increased CTP, and also tended to improve perceived voice quality. The latter effect was mostly greater in singers who did not practice singing daily. In addition, a more pronounced perceptual effect was found in singers rated as being less experienced.

Conclusion: Resonance tube phonation significantly raised CTP and tended to improve perceptual ratings of voice quality. The effect on PTP failed to reach significance.

Place, publisher, year, edition, pages
American Speech-Language-Hearing Association, 2013
Keywords
Collision threshold pressure, phonation threshold pressure, semi-occluded vocal tract, EGG, voice therapy, voice training
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-87906 (URN)10.1044/1092-4388(2013/12-0040) (DOI)000328267300016 ()
Available from: 2013-01-28 Created: 2013-01-28 Last updated: 2017-12-06Bibliographically approved
Enflo, L., Sundberg, J. & McAllister, A. (2012). Effects of vocal warm-up, vocal loading, and tube phonation on phonation and collision threshold pressures. In: Robert Sathaloff (Ed.), The Voice Foundation's 41st annual Symposium: Care of the Professional Voice. Paper presented at The Voice Foundation's 41st annual Symposium, May 30 - June 3, 2012, Philadelphia, Pennsylvania, USA. Philadelphia: The Voice Foundation
Open this publication in new window or tab >>Effects of vocal warm-up, vocal loading, and tube phonation on phonation and collision threshold pressures
2012 (English)In: The Voice Foundation's 41st annual Symposium: Care of the Professional Voice / [ed] Robert Sathaloff, Philadelphia: The Voice Foundation , 2012Conference paper, Published paper (Other academic)
Abstract [en]

Collision threshold pressure (CTP) is defined as the lowest subglottal pressure producing vocal fold collision. It has been measured in three studies, to analyze the effects of (1) vocal warm-up, (2) vocal loading and (3) the voice therapy method resonance tube phonation, which implies phonation into a tube, the end of which is placed a few cm under water. Also, phonation threshold pressure (PTP) was determined. This threshold pressure, however, although more commonly used, is often difficult to measure; the coefficient of variation has been found mostly to be higher for PTP than for CTP.

                      Before and after data for CTP and PTP were determined from audio, electroglottographic (EGG) and pressure signals. Subjects repeated the syllable /pa:/ with gradually decreasing vocal loudness at several fundamental frequencies. Subglottal pressure was estimated from oral pressure during the p-occlusion. CTP was determined using EGG or dEGG spike amplitude as criteria of vocal fold collision, while vocal fold vibration for PTP measurement was determined from the audio signal.

The first investigation, with 15 amateur singers, suggested that vocal warm-up tended to lower both CTP and PTP. The effect of vocal loading, studied in seven subjects two of whom had trained voices, was that CTP and PTP rose, especially in the untrained voices. Resonance tube phonation exercise (tube length 27 cm, Æ 8 mm) caused an increase of CTP and PTP in 12 mezzo-soprano voices, with different levels of voice training. The effect on both CTP and PTP was greater in less trained singers, and was perceived as an improvement in a pair-wise comparison listening test with seven voice experts.

The three studies support the conclusion that CTP can be used as a valuable complement to or replacement of PTP.

Place, publisher, year, edition, pages
Philadelphia: The Voice Foundation, 2012
National Category
Health Sciences
Identifiers
urn:nbn:se:liu:diva-79342 (URN)
Conference
The Voice Foundation's 41st annual Symposium, May 30 - June 3, 2012, Philadelphia, Pennsylvania, USA
Projects
Alternative measures of Phonation. Collision threshold pressure and wavegrams
Available from: 2012-07-11 Created: 2012-07-11 Last updated: 2015-09-22
Enflo, L., Sundberg, J., Romedahl, C. & McAllister, A. (2011). Effects of Tube Phonation on Collision and Phonation Threshold Pressures in Mezzo-soprano Voices. In: Antoine Giovanni & Nathalie Henrich, (Ed.), Pan European Voice Conference (PEVOC9). Paper presented at PEVOC9 Marseille, August 2011.
Open this publication in new window or tab >>Effects of Tube Phonation on Collision and Phonation Threshold Pressures in Mezzo-soprano Voices
2011 (English)In: Pan European Voice Conference (PEVOC9) / [ed] Antoine Giovanni & Nathalie Henrich,, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Tube phonation is a voice therapy method widely used in Scandinavia and Germany. Invented by Sovijärvi (1965 & 1969) in the sixties, it is now used to treat several kinds of voice pathologies but also to solve passaggio and speech problems among singers. The subject phonates into a 26-28 cm long tube, typically made of glass, with the other end placed a few cm under water in a bowl. The resulting bubbling causes a modulation of intraoral pressure. Tube phonation is supposed to contribute to the development of appropriate combinations of air flow and subglottal pressure needed for a healthy voice control and/or vocal skill.

 The present study is part of a project aiming at exploring the potentials of the collision threshold pressure (CTP) (Enflo and Sundberg, 2009; Enflo et al., 2009), defined as the lowest subglottal pressure needed for vocal fold collision. This pressure may be a valuable complement to the commonly used phonation threshold pressure (PTP), defined as the lowest subglottal pressure needed to obtain and sustain vocal fold vibration. In the present investigation we analysed the effects of tube phonation on these threshold pressures. Twelve mezzo-sopranos with differing levels of singing training participated in the experiment, six highly advanced classically trained singers with daily  singing practise, and six modestly experienced choir singers without daily  singing practise. Subglottal pressure, EGG and audio were recorded before and after a tube phonation exercise. The tube phonation induced intraoral pressure modulation amplitude of about five cm H2O. Perceptual effects of the tube phonation in these subjects was assessed by a listening test. On average across singers CTP tended to rise, particularly in the less well trained singers. The listening test indicated that tube phonation was associated with a clearly audible improvement of voice function, at least in the less well-trained singers.

Keywords
Tube phonation, collision pressure, phonation threshold pressures, female singers
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-75213 (URN)
Conference
PEVOC9 Marseille, August 2011
Available from: 2012-02-21 Created: 2012-02-21 Last updated: 2015-09-22
Enflo, L. & Sundberg, J. (2009). Vocal fold collision threshold pressure: An alternative to phonation threshold pressure?. Logopedics, Phoniatrics, Vocology, 34(4), 210-217
Open this publication in new window or tab >>Vocal fold collision threshold pressure: An alternative to phonation threshold pressure?
2009 (English)In: Logopedics, Phoniatrics, Vocology, ISSN 1401-5439, E-ISSN 1651-2022, Vol. 34, no 4, p. 210-217Article in journal (Refereed) Published
Abstract [en]

Phonation threshold pressure (PTP), frequently used for characterizing vocal fold properties, is often difficult to measure. This investigation analyses the lowest pressure initiating vocal fold collision (CTP). Microphone, electroglottograph (EGG), and oral pressure signals were recorded, before and after vocal warm-up, in 15 amateur singers, repeating the syllable /pa:/ at several fundamental frequencies with gradually decreasing vocal loudness. Subglottal pressure was estimated from oral pressure during the p-occlusion, using the audio and the EGG amplitudes as criteria for PTP and CTP. The coefficient of variation was mostly lower for CTP than for PTP. Both CTP and PTP tended to be higher before than after the warm-up. The results support the conclusion that CTP is a promising parameter in investigations of vocal fold characteristics.

Place, publisher, year, edition, pages
Informa Healthcare, 2009
Keywords
Electroglottography, fundamental frequency, phonation threshold, singing, vocal fold contact, vocal warm-up
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-87905 (URN)10.3109/14015430903382789 (DOI)
Available from: 2013-01-28 Created: 2013-01-28 Last updated: 2017-12-06
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