1.Alghamdi et al., England, 2018 |
To characterize the acoustic, phonetic, and articulatory modifications of speech in the Lombard Effect. |
54 speakers, both genders. |
Read 100 randomized sentences with noise exposure of 80 dB. |
f0, mean volume, spectral energy, mean vowel duration |
There were acoustic and articulatory changes for all participants. In the largest increase in the estimated duration of the vowel, there was a significant reduction in the frequency of the second formant. |
2.Castro et al., Chile, 2018. |
To compare the aerodynamic, biomechanical and neurophysiological acoustic parameters of healthy individuals and individuals with dysphonia when exposed to the Lombard effect. |
10 individuals, both genders, healthy and with muscle tension dysphonia. |
Pronounce a series of vowels and syllables, displayed on a screen, with and without noise of 80 dB and after using noise. |
Videolaryngoscopy, aerodynamic and acoustic measurements. |
Subjects with muscle tension dysphonia may be more sensitive to the Lombard effect and have greater difficulty returning to their usual settings. It is believed that these patients have an interrupted auditory-motor control integration during speech production. |
3.Fernandes et al., Brazil, 2018. |
Evaluate the influence of auditory feedback on voice intensity and frequency in individuals without vocal complaints |
40 women without vocal complaints. |
Producing the vowel /a/, saying the days of the week and singing before, during and after exposure to 80 dB white noise in headphones. |
Voice intensity and frequency, before, during and after exposure to noise. |
The condition of exposure to noise causes an increase in voice intensity and the interruption of exposure to noise causes a decrease in vocal intensity in women without complaints. |
4. Lijima et al., Japan, 2016. |
To investigate the effects of auditory feedback masking in a singing task. |
6 men. |
Sing a firm /a/ vowel in tones: C3, G3 and C4 for 5 seconds under 85 dB pink noise, 85 dB pink noise with a 2 kHz how pass filter and no masking. |
F0, sound pressure level and formants 1 and 2 in each condition. |
Sound pressure level and formant 1 and 2 frequencies increased under noise in both experiments. The sound pressure level and formant 1 and 2 frequencies decreased when the 2 kHz high pass filter was used. |
5. Kleber et al., Canada, 2016. |
To test how auditory feedback masking affects pitch accuracy and corresponding brain activity in trained and untrained singers. |
22 singers, (4 M e 19 F), divided into trained and untrained. |
Hear and sing tones (Between C# 3 to D5 for women and F2 and B3 for men), with and without masking inserted through headphones. |
Magnetic resonance imaging during exposure to noise. |
Pitch accuracy matching was unaffected by masking in trained singers, but decreased in non-singers. The right insula was up-regulated during masking in singers, but down-regulated in non-singers. Functional connectivity with inferior parietal, frontal, and sensorimotor areas relevant to voice increased in singers but decreased in non-singers. |
6. Yiu and Yip, China, 2015. |
Investigate the effects of environmental noise on vocal intensity and f0 using an accelerometer. |
24 young adults (2 groups of 12 F and 12 M). |
Read text, from 3 to 5 minutes, under the conditions: (1) quiet room (35.5 dB); (2) room with moderate level of ambient noise (54.5 dB); (3) a room with high ambient noise (67.5 dBA). |
Variations in F0, perception of effort, sound pressure level, and vocal dose measurements. |
Both groups showed increases in vocal intensity, F0, and perception of vocal effort in the high-noise environment compared to the other two conditions. The results support that conversation noise levels should be maintained <50-55 dB to preserve speech intelligibility. |
7. Erdemir and Rieser, USA, 2012. |
To investigate the effects of noise exposure on the control of singing abilities in trained and untrained singers. |
42 individuals; both sexes. Singer group, instrumentalist group, and non-musician group. |
To sing the same song under conditions with and without masking (conversation and music sound) played through headphones at 95dB. Participants were instructed to try to maintain vocal intensity at 80dB based on visual feedback. |
Acoustic analysis, F0 variations. |
Auditory feedback is an important factor in maintaining pitch and timing accuracy even after years of musical training. Singers relied less on auditory feedback. Instrumentalists and non-musicians were impaired by the absence of auditory feedback. |
8.Li and Jeng, China, 2011. |
To examine voice pitch maintenance during modifications in auditory feedback, observing the effects of signal-to-noise ratio at various stimulus intensities. |
12 adults (5 M e 7 F) |
To produce the vowel /i/ under six conditions of signal-to-noise ratio (12, 6, 0, 6, and 12 dB) at three different intensities of auditory masking through headphones (70, 55, and 40 dB) during phonation. |
Electroencephalography, F0 variations. |
There is a tolerance for pitch control in relation to noise. There is a minimum signal-to-noise ratio to assess pitch processing. |
9. Caldeira et al., Brazil, 2011. |
To verify and compare the occurrence of vocal modifications in reporters and non-reporters in the presence of masking noise. |
46 subjects, both sexes, allocated as follows: 23 reporters and 23 non-reporters. |
To read a passage from a newspaper article (36 words) under the following conditions: without noise, with 50 dB noise, and with 90 dB noise. The noises were introduced through headphones. |
Auditory perceptual evaluation and acoustic analysis. |
With 50 dB of masking, there was a greater increase in the pitch (82.6%), loudness (91.3%), and tension (82.6%) parameters in the control group compared to the reporters' group. The same occurred with 90 dB noise for the pitch (95.7%), loudness (100%), and tension (91.3%) parameters. Reporters demonstrated partial inhibition of the negative impact of noise situations. |
10. Grillo et al., USA, 2010. |
Explore the effects of auditory masking on laryngeal resistance when individuals produced breathy, normal, and tense voices of trained women. |
18 vocally trained women. |
Produce breathy, normal, and tense voices at 7 fundamental frequencies (220 Hz, 277 Hz, 349 Hz, 440 Hz, 554 Hz, 698 Hz, and 880 Hz) during a repeated /pi/ utterance under normal auditory feedback and masked with 104 dB noise. |
Mean and standard deviation of laryngeal resistance, aerodynamic measurements. |
The values of laryngeal resistance for breathy and normal voice remained constant in both feedback conditions, while for tense voice, they increased in the masked feedback. Tense voice may be more susceptible to the influence of auditory feedback because it is less stable than the other tested patterns. |
11. Lindstrom et al., Sweden, 2009. |
To investigate the correlations between noise level and fundamental frequency (F0) in a population of preschool teachers at their workplace. |
13 preschool teachers. |
Usual teaching activity of 3 to 4 hours of class while measuring vocal production intensity (through a microphone attached near the mouth) and the noise level of the environment (measured by a decibel meter). |
Vocal dose, sound pressure level of the voice, and local noise level. |
Vocal behavior in relation to noise exposure is highly individual based on the analyzed parameters. The reduction in noise level did not necessarily correspond to a reduction in sound pressure level emitted by the participant. |
12 Larson et al., USA, 2008. |
Test the vocal modifications in fundamental frequency (F0) and amplitude control during simultaneous perturbations of voice pitch and intensity auditory feedback. |
24 subjects tested (2 males and 22 females). |
Sustain a vowel /u/ under the following conditions: 1. Change the frequency by 0.5 semitones up or down; 2. Change the intensity by 10 dB above the produced signal; 3. Change the intensity and frequency according to the previously presented patterns. |
Modifications of intensity and F0. |
The subjects responded in the opposite direction to the frequency or intensity displacement stimuli. Depending on the direction of the stimulus, both responses can change either in the same direction or in the opposite direction to each other. |
13. Lee et al., USA, 2007. |
To investigate the relationship between auditory function and F0 using binaural masking with noise during sustained vowel vocalizations. |
8 healthy individuals (4 males and 4 females). |
Produce sustained vowel /a/ at intensities of 65 to 75 dBA and 90 to 100 dBA with and without the presence of 85 dB noise inserted through headphones. |
Modifications of F0. |
There was an increase in the frequency range of <3 Hz during the noise insertion. A negative feedback control on F0 is suggested regarding F0 modulations smaller than 3 Hz. The auditory system helps control the stability of F0 during sustained vowel production. |
14. Ferrand, EUA, 2005. |
To investigate phonatory stability by measuring changes in intensity, F0, jitter, and NHR in different noise conditions. |
22 women without complaints. |
Three sustained emissions of the vowel /a/ for each condition: 1. Noise level (0-dB ML); 2. 50 dB noise inserted through headphones; 3. 80 dB noise inserted through headphones. |
Acoustic measurements of frequency and intensity. |
There was an increase in vocal production intensity in both noise conditions. There was also an increase in fundamental frequency (F0), although it was less robust. |
15. Deliyski et al., USA, 2005. |
To investigate the influence of noise on the accuracy, reliability, and validity of acoustic measures of voice quality for gender, age, intersubject and intrasubject variability. |
20 participants of both genders. |
Produce sustained vowel /a/ for 10 seconds at 88 dB, inserted through headphones, during the presence and absence of noise at levels 42 dB above, 30 dB above, and 30 dB below the production intensity. |
Acoustic measurements. |
The results suggest that the recommended, acceptable, and unacceptable levels of noise in the acoustic environment are above 42 dB, above 30 dB, and below 30 dB signal-to-noise ratio, respectively. |
16. Mürbe et al., Germany, 2003. |
To evaluate the effect of training on singing control in legato and staccato tasks, at slow and fast tempos, in students with 3 years of musical education. |
22 trained singers, both genders. |
Sing the vowel /a/ in an ascending scale and a descending triad pattern covering your entire pitch range, with and without 105dB masking, inserted through headphones, in legato and staccato, and at a slow and fast tempo. |
F0 and comparison between intervals and pitch accuracy. |
The masking compromised the accuracy of pitch, for both staccato and legato, and for fast performance compared to slow performance. Kinesthetic feedback contributes to pitch accuracy in trained singers. |
17. Mürbe et al., Germany, 2002. |
To estimate the importance of auditory and kinesthetic feedback for voice pitch control in 28 beginner professional solo singing students. |
28 singers, both genders (17 females and 11 males). |
Sing the vowel /a/ in an ascending scale and a descending triad pattern covering your entire pitch range, with and without 105dB masking inserted through headphones, in legato and staccato, and at a slow and fast tempo. |
Measurement of F0 accuracy using software. |
The masking compromised pitch accuracy by 14% in all subjects in the conditions of fast tempo, staccato, and legato. Auditory feedback contributes to the pitch control of singers. |
18. Tonkinson, USA, 1994. |
To compare the level of vocal intensity response of adult singers with different training durations before and after verbal instructions to resist the Lombard Effect while singing with a pre recorded tape of a choir singing. |
27 individuals of both genders. |
Sing and ignore, through verbal commands, the Lombard Effect produced by inserting audio, through headphones, at intensities of 80 to 100 dB, containing recordings of other people singing the same musical excerpt. |
Sound pressure level. |
Both groups were able to resist the Lombard Effect based on simple commands given by the evaluator. |
19. Herbert et al., USA, 1988. |
To test the resistance to the Lombard Effect when individuals are instructed and trained with visual feedback to suppress it. |
24 students, both genders, assigned to: G1 (constant vocal intensity for 2 minutes alternating periods of silence and noise with visual feedback to resist the Lombard Effect), G2 (same instructions as G1, but without feedback), G3 (no instruction or visual feedback). |
Speak spontaneously during the session for 20 minutes while receiving white noise of 90 dB through headphones. |
Variations in speech intensity. |
Individuals who had visual support were able to inhibit the Lombard response, and the inhibition remained after the visual feedback was removed. The Lombard response is largely automatic and involuntary. |
Sidetone Effect
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1. Nudelman et al., USA, 2021. |
To examine the effects of auditory feedback amplification through bone conduction on acoustic vocal parameters and subjective self-assessment of vocal effort in patients with vocal disorders. |
47 dysphonic individuals (14 males and 13 females). |
Perform reading of texts under three conditions: auditory feedback amplification at 54 dB HL and 58 dB HL, and without amplification. Amplification was done through a microphone and headphones. |
Self-perceived and recorded vocal effort on a visual analog scale (EVA), vocal sound pressure level adaptation level. |
There is a consistent positive adaptation in sound pressure level for vocal hyperfunction, glottic insufficiency, and laryngeal pathologies when subjected to an amplification task with higher intensity (58dB). |
2. Tomassi et al., USA, 2021. |
To determine the therapeutic potential of amplification effects on vocal function during audiovisual telecommunications. |
18 participants (8 males and 10 females). |
Conversation task under three conditions: without amplification, with low sidetone amplification, and with high sidetone amplification, for 10 minutes. |
Vocal intensity, vocal quality, and self-perceived effort. |
There were decreases in vocal intensity during the auditory feedback amplification condition, and participants perceived less vocal effort during the amplification. Results indicated a possible improvement in vocal quality. |
3. Assad et al., Brazil, 2017. |
To determine if voice amplification influences vocal dose in female teachers with dysphonia. |
15 female teachers with functional dysphonia. |
Two assessment moments. 1st Moment: Teaching with a portable electronic sound amplification system for 92 minutes; 2nd Moment: Teaching without a sound amplification system for 92 minutes. |
Intensity, fundamental frequency, phonation percentage, cyclic dose, and distance dose. |
The use of vocal amplification in teachers results in a reduction in F0 (fundamental frequency) and voice intensity. The cyclic dose and distance dose show that amplification allows the teacher to maintain the same phonation time but decreases the number of vocal fold oscillations (cyclic dose) and the total distance traveled by the vocal fold tissue during phonation (distance dose), reducing vocal fold exposure to vocal trauma. |
4. Gaskill et al., USA, 2011. |
To determine the effect of a portable voice amplifier on vocal dose in teachers with and without vocal complaints. |
2 teachers, one with vocal complaints and one without vocal complaints. |
Teach for one week with and one week without the use of a portable voice amplification system, while using a vocal dosimeter throughout the experiment. Each week lasted for five days, with one session per day. |
Cyclic, dose distance and intensity. |
The use of the amplifier was effective in reducing vocal load due to the decrease in speech intensity. Amplification reduces the distance dose and appears to decrease the cyclic dose. |
5. Nsdottira et al., Iceland, 2003. |
To investigate changes in teachers' voice quality during two situations: a regular workday under normal conditions and another with sound amplification. |
5 teachers (3 females and 2 males). |
Teach during the most challenging workday under both normal conditions and amplified conditions using a microphone system and loudspeaker calibrated to a maximum signal of 80dB. Recordings were conducted during the first and last class of the teacher's shift, each lasting 40 minutes. |
F0 (fundamental frequency), sound pressure level, and questionnaires containing the participants' opinions and acoustic analysis. |
The teachers reported less fatigue when using the amplifier. The recorded voices, during the use of the amplifier, were considered less tense. In the acoustic analysis, a decrease in spectral tilt was found in the voices that used the amplifier. |
6. McCormick et al., USA, 2002. |
To examine the effectiveness of the ChatterVox Portable Voice Amplification System (Siemens Hearing Instruments) in reducing the sound pressure level (SPL) of speakers' voices during a simulated lecture in the classroom. |
10 speakers. |
Read phonetically balanced text using a voice amplifier coupled to sound return boxes. The participant had the auditory feedback amplified for 2 minutes of reading and in the middle of the task the amplification was turned off and the participant read for another 2 minutes. The level of voice adaptation was measured close to the mouth and at the back of the room. |
Voice intensity measurements. |
There was a mean decrease in vocal intensity at the level of the mouth of 6.03 dB SPL and a mean increase of 2.55 dB SPL at the back of the room. The ChatterVox amplification device reduces the vocal intensity level at the microphone. |
7. Jónsdottir et al., Finland, 2002. |
To investigate changes in speech during a teacher's working day under normal conditions and when using a voice amplification device. |
3 female teachers and 2 male teachers |
Teaching during a day of intense work under normal conditions and amplified by a microphone and speaker system calibrated for a maximum signal of 80dB. The recordings were made in the first and last class of the teacher's shift, lasting 40 minutes each. |
F0, sound pressure level and questionnaires containing the participants' opinion. |
An increase in F0 and sound pressure level was found during the experiment, but the change was greater in F0 when amplification was used. All teachers reported less vocal fatigue when using amplification. The results support the suggestion that an increase in F0 and sound pressure level are not just a sign of vocal fatigue, but may even reflect an adequate adaptation to vocal demand. |
8. Jónsdóttir, Iceland, 2002. |
Verify whether the use of sound amplification in the classroom has beneficial effects on teachers' vocal production and resistance Determine the negative effects of amplification on the speaker and listener. |
33 teachers and 791 students. |
Teachers taught with and without voice amplification for one week in each condition. The amplification system was through lapel microphones and the reception through external speakers. |
Students' perception and teachers' self-perception. |
97% of teachers reported easier voice production, 82% improved vocal endurance. 84% of students found it easier to listen and 63% of students found concentration improved when amplification was used. The negative points reported by teachers and students were technical problems with the devices. |
9. Laukkanen et al., Finland, 2002. |
Investigate the effects of HearFones through self-perception, auditory and acoustic perceptive analysis on the received intensity, voice quality in singing, vocalization and reading tasks. |
Test 1: 2F and 2M. Test 2: 9F, 4 M. Test 3: 6 speech therapists. |
Tests: 1 - Text reading sample with and without HearFones. 2 – Singing sample with and without headphones. 3 – Emission of the vowel /pa/, text reading and singing, with and without HearPhones. |
Acoustic analysis, electroglottography, auditory perceptive analysis, self-perception of quality and vocal comfort. |
HearFones seems to improve voice harmonics, decrease vocal intensity. Participants perceived their voices as “less strained” and “better in control”. Electroglottography indicated better glottic closure and/or decreased activity of the thyroarytenoid muscle while using the device. |
10. Roy et al., USA, 2002. |
Compare the effects of guidance on vocal hygiene versus voice amplification in teachers with voice problems. |
44 teachers with vocal complaints, divided into 3 groups: control group, vocal hygiene group and portable sound amplifier group (Chatter-Vox). |
Participants in each group were instructed to use vocal hygiene strategies, amplifier use or no intervention according to their allocation in the group for six weeks. |
Self-perception of voice handicap and severity of the voice problem and perception of the strategy used, acoustic and auditory perceptive analysis. |
There were no differences between the sound amplification and vocal hygiene groups. The amplification group reported greater clarity and greater ease of voice production with greater adherence to the proposed strategy. The findings support the clinical utility of sound amplification as an alternative for the rehabilitation of vocal problems in teachers. |
11. Nsdottir et al., Finland, 2000. |
Test whether sound amplification reduces the vocal production load. |
5 women. |
Reading text of 133 words under normal circumstances, hearing your own amplified voice, through headphones and with auditory feedback dampened by foam earplugs inserted in the external auditory canal. |
Acoustic modifications of F0 and sound pressure level. |
The F0, sound pressure level and the first formant decreased during amplified and damped feedback. The results suggest that both amplification and damping of auditory feedback can reduce vocal load during phonation. |
12.Chang-Yit et al., USA, 1975. |
Evaluate the effect and stability of own voice amplification under different amplification conditions over time. |
Experiment 1 = 9 college students; experiment 2 = 6 university students. |
Experiment 1: spontaneous speech for 12 min while the voice was amplified by 20dB; experiment 2: spontaneous speech for 6 min while the voice was amplified by 20dB or 10dB and speech for 6 minutes while the voice was amplified and 80 dB noise was added. Experiment 2 was repeated for 5 days. |
Sound pressure level modifications in voice modification. |
The compensatory adjustment in voice in experiment 1 was the reduction from 7 dB to 20 dB of amplification. In experiment 2 the effect was the same in all repetitions of the experiment. The continuous presentation of noise does not desensitize the subject to the effect of inserting noise. The amplification effect is a component of speech regulation. |
Sidetone and Lombard Effects
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Main findings and conclusion
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1. Bottalico et al., USA, 2016. |
Evaluate the effects on pitch inaccuracy between the reference notes and the note sung under the conditions: 1) level of external feedback, (2) tempo (slow or fast), (3) articulation (legato or staccato), (4) tessitura (low, medium, or high) and (5) semi-phrase direction (ascending or descending). |
20 subjects, both sexes, divided into professional and semi-professional singers. |
Singing repetitions of arpeggios at different tempos and articulations under the conditions of unaltered feedback, feedback augmented by reflective panels, and feedback diminished by earplugs. |
Tuning accuracy. |
The inaccuracy was greater when the tempo was faster and the articulation was staccato in semi-professional singers. However, professional singers were more accurate in the diminished feedback condition than in the other external feedback conditions. With increasing training, the inaccuracy of the singer's pitch decreases. |
2. Bottalico et al., USA, 2015. |
To analyze the Lombard effect, the relationship between sound pressure level and auditory feedback, the relationship between voice quality and external auditory feedback, level of accompaniment, voice register and the singer's gender in professional and non-professional singers. |
10 amateur singers and 10 professional singers of both sexes. |
Singing excerpts of the same song under the following conditions: unaltered auditory feedback, amplification and reduction of auditory feedback while using a musical accompaniment at three levels (70, 80 and 90 dBA) inserted through headphones. |
F0, voice quality. |
The Lombard effect was strongest for amateurs, higher levels of external auditory feedback were associated with a reduction in sound pressure level, and this effect was strongest in amateur singers. Better voice quality was detected in the presence of higher levels of external auditory feedback. |
3. Bottalico et al., USA, 2015. |
Evaluate the effects of voice style (soft, normal and loud), background noise level and external auditory feedback on vocal effort and self-reported vocal comfort, control and vocal fatigue. |
20 subjects with no complaints. |
Reading a text in a soft, normal and loud way, lasting between 1 and 2 minutes, in a semi-reverberant room with and without panels that increase auditory feedback, and in noise conditions of 40 dB and 61 dB. |
Self-perception of fatigue, comfort and vocal control. |
Participants increased their level of fatigue in the presence of noise and when instructed to speak in a loud style. They lessened fatigue when feedback was increased and when speaking in a smooth style. In self-perception, there was a preference for the normal style without noise. |
4. Siegel and Pick, USA,1995. |
Check changes in sound pressure level when there is an increase or decrease in auditory feedback, in the presence or absence of noise under normal or instructed conditions to compensate for changes. |
20 individuals of both sexes. |
Speak spontaneously while amplifying or reducing the auditory feedback of your voice by 20 dB. First instruction: carry out the necessary compensations for the different types of manipulation. In the second instruction: do not change the sound pressure level in view of the modifications. |
Changes in sound pressure level. |
The reduction or amplification effect was greater when subjects were instructed to compensate for changes in volume changes. The presence of noise increased the subjects' compensation responses. The presence of noise increases response to auditory feedback manipulations. |