Effect of Noise on Vocal Loudness and Pitch in Natural Environments: An Accelerometer (Ambulatory Phonation Monitor) Study Edwin M-L. Yiu and Priscilla, P. S. Yip, Pokfulam, Hong Kong Summary: Purpose. This study investigated the effects of environmental noise on the production of vocal intensity and fundamental frequency using an accelerometer. Methods. Twenty-four vocally healthy young adults (12 men and 12 women, aged 19–22 years) recorded a monologue passage using KayPENTAX (Montvale, NJ, USA) Ambulatory Phonation Monitor (model 3200) under three natural environmental conditions in a randomized order: a quiet room (mean noise, 35.5 dBA), room with moderate level of noise (mean noise, 54.5 dBA), and a room with high noise (mean noise, 67.5 dBA). Results. Both gender groups showed significant increases in the mean vocal intensity, fundamental frequency, and perceived vocal effort in the high-noise environment than in the other two conditions. No significant difference was found in the vocal intensity between the quiet and moderately noisy environment except in the fundamental frequency in the female group. Conclusions. This study showed that the use of accelerometer for laryngeal signal recordings could be a useful tool for measuring phonation without being affected by the background noise. The findings also support the recommendation that noise levels for conversation should be kept 0.05).
DISCUSSION The objective of this study was to examine the effects of natural environmental noise on the production of vocal intensity, fundamental frequency, and self-perceived vocal effort in individuals with normal healthy voice. Both the female and male participants demonstrated significantly higher vocal intensity, fundamental frequency, and vocal effort when the mean background noise increased from 35.5 dBA (quiet clinic room) to 67.5 dBA (pantry room). The findings are consistent with those from the studies conducted using microphones in the laboratory and free field settings.8,11,14 Lombard effects were demonstrated under situations with high-background-noise levels. The participants in the present study reported that they used more vocal effort to overcome the background noise. They automatically increased their vocal loudness, with the fundamental frequency also increased, probably as a consequence of increase in subglottal pressure.3,24 It should be noted that when the background noise was at a level of 54.5 dBA, both gender groups showed little changes in the vocal intensity, fundamental frequency, or vocal effort when compared with those at 35.5 dB. According to the International Organization for Standardization,25 with a 55-dBA noise level, the speech intelligibility for a normal conversational speech at 1 m is around 95% (p.358). Therefore, the intelligibility was still acceptable and it therefore probably did not prompt the speakers to increase their vocal function and effort to increase the intelligibility for maintaining the communication. The high-noise-level condition (67.5 dBA) led to a significantly greater perception of vocal effort. In theory, the mechan-
ical loading on the vocal fold tissues would correspondingly increase because of high fundamental frequency and vocal intensity during phonation,26 which might result in an increase in perceived vocal effort. The male group in general perceived a significantly greater vocal effort than the female group in voice production under all three levels of noise situations. It is unclear why such vocal effort is perceived generally higher by the male speakers than by the female speakers. It might well be that there was a sampling bias in the present study in which only 12 subjects in each group were recruited or the male speakers in general feel they have to put in more vocal effort to speak efficiently. This result was different from the laboratory findings reported by S€odersten et al.11 They found a higher level of vocal effort in the female group compared with a male group. There were three methodological differences between the two studies; one was related to the use of different rating scales. The present study used an 11-point rating scale, whereas the study by S€odersten et al11 used a 100mm visual analog scale. However, it is hard to anticipate that the use of different scales would lead to such gender difference. The second difference was in the use of a higher noise levels (range, 70–80 dBA) in the study by S€odersten et al,11 compared with 66–69 dBA in the present study. Such a difference still would not be able to explain why the male speakers perceived their vocal effort to be relatively high (4.08; Table 1) even when the noise level was kept at 35.5 dBA level. The third difference was the sample characteristics related to the age and fundamental frequencies of the subjects. In the present study, the mean age of the female and male age-matched subjects was 21.2 years, whereas those in the study of S€odersten et al11 were 44 years and 34 years for the female and male groups, respectively. Furthermore, the female and male subjects in the present study showed a mean fundamental frequency of 204 and 124 Hz, respectively, in a quiet condition, whereas those from the study of S€odersten et al11 showed a mean fundamental frequency of 231 and 143 Hz, respectively. Whether the differences in age and speaking fundamental frequency demonstrated by the subjects between the Chinese group in the present study and the Swedish group11 might have contributed to their different perception of vocal effort in response to noises could not be ascertained with the available data. Apart from these two physical factors (age and speaking fundamental frequency), the
Edwin M-L. Yiu and Priscilla, P.S. Yip
Vocal Loudness and Pitch in Natural Environments
social factors of cultural difference and gender preference might have play a role in their reaction to noise. There is currently very little information on these social factors. Further investigations will be needed to verify these. Another objective of the present study was to examine the correlation between vocal fundamental frequency/intensity and perceived vocal effort ratings. Significant low to moderate correlations were only found between the vocal fundamental frequency and the perceived vocal effort (male: r ¼ 0.455, P < 0.01; and female: r ¼ 0.37, P < 0.05), but no significant correlation was found between vocal intensity and perceived vocal effort ratings. This suggests that the fundamental frequency probably has something to do with increasing or decreasing vocal effort in voice production. In summary, this study showed that a high level of background noise could bring about a significant increase in the vocal fundamental frequency and intensity in both male and female speakers. Such Lombard effect was significant when the noise levels reached a level beyond 67.5 dBA. The findings from this study showed that background noise exerts adverse effects on voice production when the noise level was beyond 60 dBA, whereas little or no effect when the noise was below 56 dBA. One should be cautious, however, in overgeneralizing the findings of the present study. Only young adults aged from 19 to 22 years were recruited in this study. The sample recruited was not representative of the general population. With this young people, Lombard effect was only noticed when the background noise increased to >60 dB. Whether people of other age group with different hearing acuity would respond differently or not would required further study. As high fundamental frequency and vocal intensity would have detrimental effects on the vocal fold tissues, prolonged use of voice under noisy environments would increase the risk of developing voice problems. It warrants concern for the individuals who spend time working or speaking under highbackground-noise environments, such as in restaurants and transportations. It is important to avoid prolonged speaking under these noise environments. Acknowledgments This study was supported in part by a grant from the Hong Kong Research Grant Council 2007 General Research Fund (HKU#753007) and the Quality Education Fund 2008 (EDB/ QEF/2006/0127). The authors would like to acknowledge that the Ambulatory Phonation Monitor unit is provided by KayPENTAX for research purposes. REFERENCES 1. Siegel GM, Pick HL. Auditory feedback in the regulation of voice. J Acoust Soc Am. 1974;56:1618–1624. 2. Lane H, Tranel B. The Lombard sign and the role of hearing in speech. J Speech Hear Res. 1971;14:677–709.
5
3. Gramming P, Sunberg J, Ternstrom S, Leanderson R, Perkins W. Relationship between changes in voice pitch and loudness. J Voice. 1988;2: 118–126. 4. Vilkman E, Lauri ER, Alku P, Sala E, Sihvo M. Ergonomic conditions and voice. Logoped Phoniatr Vocol. 1998;23:11–20. 5. Vilkman E. Voice problems at work: a challenge for occupational safety and health arrangement. Folia Phoniatr Logop. 2000;52:120–125. 6. Junqua JC. The Lombard reflex and its role on human listeners and automatic speech recognizers. J Acoust Soc Am. 1993;93:510–524. 7. Pittman AL, Wiley TL. Recognition of speech produced in noise. J Speech Lang Hear Res. 2001;44:487–496. 8. Tartter VC, Gomes H, Litwin E. Some acoustic effects of listening to noise on speech production. J Acoust Soc Am. 1993;94:2437–2440. 9. Van Summers W, Pisoni D, Bernacki R, Pedlow R, Stokes M. Effects of noise on speech production: acoustic and perceptual analyses. J Acoust Soc Am. 1988;84:917–928. 10. Letowski T, Frank T, Caravella J. Acoustical properties of speech produced in noise presented through supra-aural earphones. Ear Hear. 1993;14: 332–338. 11. S€odersten M, Ternstr€om S, Bohman M. Loud speech in realistic environmental noise: phonetogram data, perceptual voice quality, subjective ratings, and gender differences in healthy speakers. J Voice. 2005;19:29–46. 12. Pearsons K, Bennett L, Fidell S. Speech Levels in Various Noise Environments. Washington, DC: Office of Health and Ecological Effects, Rep. No. EPA-600/1-77-025; 1977. 13. Sala E, Airo E, Olkinuora P, et al. Vocal loading among day care center teachers. Logoped Phoniatr Vocol. 2002;27:21–28. 14. S€odersten M, Granqvist S, Hammarberg B, Szabo A. Vocal behavior and vocal loading factors for preschool teachers at work studied with binaural DAT recordings. J Voice. 2002;16:356–371. 15. Eustace CS, Stemple JC, Lee L. Objective measures of voice production in patients complaining of laryngeal fatigue. J Voice. 1996;10:146–154. 16. Gotaas C, Starr CD. Vocal fatigue among teachers. Folia Phoniatr (Basel). 1993;45:120–129. 17. Hillman R, Cheyne H. A portable vocal accumulator with biofeedback capability. In: Schade G, Muller F, Wittenberg T, Hess M, eds. AQL Hamburg: Proceeding Papers for the Conference Advances in Quantitative Laryngology, Voice and Speech Research. Stuttgart, Germany: IRB Verlag; 2003. 18. Nacci A, Fattori B, Mancini V, Panicucci E, Ursino F, Cartaino FM, Berrettini S. The use and role of the Ambulatory Phonation Monitor (APM) in voice assessment. Acta Otorhinolaryngol Ital. 2013;33:49–55. 19. Franca MC, Wagner JF. Effects of vocal demands on voice performance of student singers. J Voice. 2015;29:324–332. 20. Cantarella G, Iofrida E, Boria P, et al. Ambulatory phonation monitoring in a sample of 92 call center operators. J Voice. 2014;28:393. e1–6. 21. Szabo Portela A, Hammarberg B, S€odersten M. Speaking fundamental frequency and phonation time during work and leisure time in vocally healthy preschool teachers measured with a voice accumulator. Folia Phoniatr Logop. 2013;65:84–90. 22. Misono S, Banks K, Gaillard P, Goding GS Jr, Yueh B. The clinical utility of vocal dosimetry for assessing voice rest. Laryngoscope. 2015;125: 171–176. 23. Yiu EM-L, Chan RM-M. Effect of hydration and vocal rest on the vocal fatigue in amateur karaoke singers. J Voice. 2003;17:216–227. 24. Alku P, Vintturi J, Vilkman E. Measuring the effect of fundamental frequency raising as a strategy for increasing vocal intensity in soft, normal and loud phonation. Speech Comm. 2002;38:321–334. 25. International Organization for Standardization. Assessment of Noise With Respect to its Effect of the Intelligibility of Speech ISO/TR 3352. Geneve, Switzerland: International Organization for Standardization; 1974. 26. Jiang J, Titze I. Measurement of vocal fold intraglottal pressure and impact stress. J Voice. 1994;8:132–144.
DISCUSSION The objective of this study was to examine the effects of natural environmental noise on the production of vocal intensity, fundamental frequency, and self-perceived vocal effort in individuals with normal healthy voice. Both the female and male participants demonstrated significantly higher vocal intensity, fundamental frequency, and vocal effort when the mean background noise increased from 35.5 dBA (quiet clinic room) to 67.5 dBA (pantry room). The findings are consistent with those from the studies conducted using microphones in the laboratory and free field settings.8,11,14 Lombard effects were demonstrated under situations with high-background-noise levels. The participants in the present study reported that they used more vocal effort to overcome the background noise. They automatically increased their vocal loudness, with the fundamental frequency also increased, probably as a consequence of increase in subglottal pressure.3,24 It should be noted that when the background noise was at a level of 54.5 dBA, both gender groups showed little changes in the vocal intensity, fundamental frequency, or vocal effort when compared with those at 35.5 dB. According to the International Organization for Standardization,25 with a 55-dBA noise level, the speech intelligibility for a normal conversational speech at 1 m is around 95% (p.358). Therefore, the intelligibility was still acceptable and it therefore probably did not prompt the speakers to increase their vocal function and effort to increase the intelligibility for maintaining the communication. The high-noise-level condition (67.5 dBA) led to a significantly greater perception of vocal effort. In theory, the mechan-
ical loading on the vocal fold tissues would correspondingly increase because of high fundamental frequency and vocal intensity during phonation,26 which might result in an increase in perceived vocal effort. The male group in general perceived a significantly greater vocal effort than the female group in voice production under all three levels of noise situations. It is unclear why such vocal effort is perceived generally higher by the male speakers than by the female speakers. It might well be that there was a sampling bias in the present study in which only 12 subjects in each group were recruited or the male speakers in general feel they have to put in more vocal effort to speak efficiently. This result was different from the laboratory findings reported by S€odersten et al.11 They found a higher level of vocal effort in the female group compared with a male group. There were three methodological differences between the two studies; one was related to the use of different rating scales. The present study used an 11-point rating scale, whereas the study by S€odersten et al11 used a 100mm visual analog scale. However, it is hard to anticipate that the use of different scales would lead to such gender difference. The second difference was in the use of a higher noise levels (range, 70–80 dBA) in the study by S€odersten et al,11 compared with 66–69 dBA in the present study. Such a difference still would not be able to explain why the male speakers perceived their vocal effort to be relatively high (4.08; Table 1) even when the noise level was kept at 35.5 dBA level. The third difference was the sample characteristics related to the age and fundamental frequencies of the subjects. In the present study, the mean age of the female and male age-matched subjects was 21.2 years, whereas those in the study of S€odersten et al11 were 44 years and 34 years for the female and male groups, respectively. Furthermore, the female and male subjects in the present study showed a mean fundamental frequency of 204 and 124 Hz, respectively, in a quiet condition, whereas those from the study of S€odersten et al11 showed a mean fundamental frequency of 231 and 143 Hz, respectively. Whether the differences in age and speaking fundamental frequency demonstrated by the subjects between the Chinese group in the present study and the Swedish group11 might have contributed to their different perception of vocal effort in response to noises could not be ascertained with the available data. Apart from these two physical factors (age and speaking fundamental frequency), the
Edwin M-L. Yiu and Priscilla, P.S. Yip
Vocal Loudness and Pitch in Natural Environments
social factors of cultural difference and gender preference might have play a role in their reaction to noise. There is currently very little information on these social factors. Further investigations will be needed to verify these. Another objective of the present study was to examine the correlation between vocal fundamental frequency/intensity and perceived vocal effort ratings. Significant low to moderate correlations were only found between the vocal fundamental frequency and the perceived vocal effort (male: r ¼ 0.455, P < 0.01; and female: r ¼ 0.37, P < 0.05), but no significant correlation was found between vocal intensity and perceived vocal effort ratings. This suggests that the fundamental frequency probably has something to do with increasing or decreasing vocal effort in voice production. In summary, this study showed that a high level of background noise could bring about a significant increase in the vocal fundamental frequency and intensity in both male and female speakers. Such Lombard effect was significant when the noise levels reached a level beyond 67.5 dBA. The findings from this study showed that background noise exerts adverse effects on voice production when the noise level was beyond 60 dBA, whereas little or no effect when the noise was below 56 dBA. One should be cautious, however, in overgeneralizing the findings of the present study. Only young adults aged from 19 to 22 years were recruited in this study. The sample recruited was not representative of the general population. With this young people, Lombard effect was only noticed when the background noise increased to >60 dB. Whether people of other age group with different hearing acuity would respond differently or not would required further study. As high fundamental frequency and vocal intensity would have detrimental effects on the vocal fold tissues, prolonged use of voice under noisy environments would increase the risk of developing voice problems. It warrants concern for the individuals who spend time working or speaking under highbackground-noise environments, such as in restaurants and transportations. It is important to avoid prolonged speaking under these noise environments. Acknowledgments This study was supported in part by a grant from the Hong Kong Research Grant Council 2007 General Research Fund (HKU#753007) and the Quality Education Fund 2008 (EDB/ QEF/2006/0127). The authors would like to acknowledge that the Ambulatory Phonation Monitor unit is provided by KayPENTAX for research purposes. REFERENCES 1. Siegel GM, Pick HL. Auditory feedback in the regulation of voice. J Acoust Soc Am. 1974;56:1618–1624. 2. Lane H, Tranel B. The Lombard sign and the role of hearing in speech. J Speech Hear Res. 1971;14:677–709.
5
3. Gramming P, Sunberg J, Ternstrom S, Leanderson R, Perkins W. Relationship between changes in voice pitch and loudness. J Voice. 1988;2: 118–126. 4. Vilkman E, Lauri ER, Alku P, Sala E, Sihvo M. Ergonomic conditions and voice. Logoped Phoniatr Vocol. 1998;23:11–20. 5. Vilkman E. Voice problems at work: a challenge for occupational safety and health arrangement. Folia Phoniatr Logop. 2000;52:120–125. 6. Junqua JC. The Lombard reflex and its role on human listeners and automatic speech recognizers. J Acoust Soc Am. 1993;93:510–524. 7. Pittman AL, Wiley TL. Recognition of speech produced in noise. J Speech Lang Hear Res. 2001;44:487–496. 8. Tartter VC, Gomes H, Litwin E. Some acoustic effects of listening to noise on speech production. J Acoust Soc Am. 1993;94:2437–2440. 9. Van Summers W, Pisoni D, Bernacki R, Pedlow R, Stokes M. Effects of noise on speech production: acoustic and perceptual analyses. J Acoust Soc Am. 1988;84:917–928. 10. Letowski T, Frank T, Caravella J. Acoustical properties of speech produced in noise presented through supra-aural earphones. Ear Hear. 1993;14: 332–338. 11. S€odersten M, Ternstr€om S, Bohman M. Loud speech in realistic environmental noise: phonetogram data, perceptual voice quality, subjective ratings, and gender differences in healthy speakers. J Voice. 2005;19:29–46. 12. Pearsons K, Bennett L, Fidell S. Speech Levels in Various Noise Environments. Washington, DC: Office of Health and Ecological Effects, Rep. No. EPA-600/1-77-025; 1977. 13. Sala E, Airo E, Olkinuora P, et al. Vocal loading among day care center teachers. Logoped Phoniatr Vocol. 2002;27:21–28. 14. S€odersten M, Granqvist S, Hammarberg B, Szabo A. Vocal behavior and vocal loading factors for preschool teachers at work studied with binaural DAT recordings. J Voice. 2002;16:356–371. 15. Eustace CS, Stemple JC, Lee L. Objective measures of voice production in patients complaining of laryngeal fatigue. J Voice. 1996;10:146–154. 16. Gotaas C, Starr CD. Vocal fatigue among teachers. Folia Phoniatr (Basel). 1993;45:120–129. 17. Hillman R, Cheyne H. A portable vocal accumulator with biofeedback capability. In: Schade G, Muller F, Wittenberg T, Hess M, eds. AQL Hamburg: Proceeding Papers for the Conference Advances in Quantitative Laryngology, Voice and Speech Research. Stuttgart, Germany: IRB Verlag; 2003. 18. Nacci A, Fattori B, Mancini V, Panicucci E, Ursino F, Cartaino FM, Berrettini S. The use and role of the Ambulatory Phonation Monitor (APM) in voice assessment. Acta Otorhinolaryngol Ital. 2013;33:49–55. 19. Franca MC, Wagner JF. Effects of vocal demands on voice performance of student singers. J Voice. 2015;29:324–332. 20. Cantarella G, Iofrida E, Boria P, et al. Ambulatory phonation monitoring in a sample of 92 call center operators. J Voice. 2014;28:393. e1–6. 21. Szabo Portela A, Hammarberg B, S€odersten M. Speaking fundamental frequency and phonation time during work and leisure time in vocally healthy preschool teachers measured with a voice accumulator. Folia Phoniatr Logop. 2013;65:84–90. 22. Misono S, Banks K, Gaillard P, Goding GS Jr, Yueh B. The clinical utility of vocal dosimetry for assessing voice rest. Laryngoscope. 2015;125: 171–176. 23. Yiu EM-L, Chan RM-M. Effect of hydration and vocal rest on the vocal fatigue in amateur karaoke singers. J Voice. 2003;17:216–227. 24. Alku P, Vintturi J, Vilkman E. Measuring the effect of fundamental frequency raising as a strategy for increasing vocal intensity in soft, normal and loud phonation. Speech Comm. 2002;38:321–334. 25. International Organization for Standardization. Assessment of Noise With Respect to its Effect of the Intelligibility of Speech ISO/TR 3352. Geneve, Switzerland: International Organization for Standardization; 1974. 26. Jiang J, Titze I. Measurement of vocal fold intraglottal pressure and impact stress. J Voice. 1994;8:132–144.
