The voice as a working tool. What research says about the vocal load on teachers in noise

The first lesson starts calmly: the teacher speaks in a normal voice and the whole room hears him. By the third period there is group work, break-time noise in the corridor, ventilation running, chairs scraping the floor - and the voice already has to be raised to deliver the simplest instruction. By the sixth lesson the same message costs still more: the throat is dry, speaking takes effort, and by evening the voice sounds different from the morning. Teachers describe this as routine, not as an exception. So it is worth asking a question that rarely reaches the minutes of a staff meeting: does vocal fatigue come only from how a teacher speaks, or also from where they have to be heard?

The voice is a working tool

Teaching belongs to the group of occupations in which the voice is the primary tool of the job. It is not the sheer number of words spoken that matters, but the conditions in which they are produced. An ordinary conversation happens at close range, against a steady background, with the option to interrupt and clarify. A lesson is different: the message has to reach the whole room, including the furthest desk, often amid movement, group work or brief transitions between tasks.

The voice does several jobs at once. It conveys content, it organises work - signalling the start and end of a task, structuring the lesson - and it builds relationships: intonation, pace and timbre tell a pupil whether the situation is calm or urgent. When the voice starts to fail, it is not only audibility that shrinks but the range of these functions: nuance becomes harder, holding attention without raising the volume becomes harder, and so does sustaining longer stretches of speech.

This is a description of working conditions, not a diagnosis. Most teachers work without lasting voice problems. That does not mean, however, that the effort put into speaking is the same in every room and every lesson - and it is that difference in effort the rest of this text is about.

What happens when the voice competes with noise

People speak more loudly when their surroundings get louder. This is known as the Lombard effect and is a normal, largely reflexive response of the speech system - not a disorder and not a sign of poor technique. We raise the level of the voice and slightly change its pitch and articulation so the message cuts through the background. It often happens without a conscious decision: the speaker realises only afterwards that for the last few minutes they have been speaking far louder than usual.

Two concepts that are easily confused are worth separating. Voice level is the measurable intensity of the sound the speaker produces - something that can be recorded in decibels. Vocal effort is the outlay needed to produce that utterance: muscular tension, breathing, the subjective sense that speaking is “harder going”. The two usually rise together, but they are not the same and are not measured in the same way.

Raising the voice improves the balance only partly. Louder speech is more audible, but it removes neither reverberation nor background sound - and it puts more energy into the room, which also reflects. If, in response to a louder teacher, conversation in the class also gets louder, the background level rises with the signal and the voice’s advantage over the background does not necessarily grow. We describe this mechanism more fully in the article on reverberation and speech intelligibility in the classroom.

Noise, reverberation and class size are different things

In conversations about schools all these elements merge into a single “it’s loud”. To assess working conditions they have to be separated, because they are measured separately and influenced separately.

• Noise level during lessons - the sound level in the room during class, including the voices of pupils and teacher.
• Background noise - the sound level in an unoccupied room: building services, ventilation, road traffic, the corridor, neighbouring rooms.
• Reverberation time - how fast sound decays after the source stops; a property of the room itself, independent of how loudly people speak in it.
• The number of people in the room - affects both noise level and reverberation (people absorb sound), but is not itself an acoustic parameter.
• The teacher’s speaking time - what proportion of the lesson is phonation; a measure of occupational load, not a property of the room.
• Voice level - the intensity of the sound produced by the speaker.
• Subjective difficulty of communication - how hard the teacher finds it to be understood in that room.

These factors interact: longer reverberation raises the background level, a higher background forces louder speech, a larger group generates more sound. They are not, however, identical, and a finding about one cannot be treated as evidence about the others. In particular, there is no basis for calling class size in itself a direct cause of voice disorders.

From effort to fatigue - and where self-report ends

The next distinction concerns what happens to the voice over the working day. Terms used colloquially as synonyms describe different things.

Vocal effort is the outlay needed to produce speech under given conditions. Vocal fatigue is a progressive decline in perceived vocal capacity: needing more effort for the same result, a sense of tension or dryness, a need for rest, sometimes a change in sound. Hoarseness is an audible change in voice quality that may appear temporarily and resolve on its own. Symptoms reported by a teacher are self-report information - important, but not the product of a clinical examination. Dysphonia is a term for a disorder of voice function and is not the same as a one-off bout of hoarseness. A clinically diagnosed voice disorder exists when a specialist has diagnosed it after examination. Finally, mental load and cognitive fatigue are a separate dimension: working in difficult acoustic conditions can be mentally tiring regardless of how the voice sounds.

The order of this list is not a path of illness. Raised vocal effort does not mean a teacher is on the way to dysphonia, and tiredness after a day’s work is not a diagnosis. Symptoms change over the day - they build after lessons that demand more speaking and ease after a period of quiet. Rest reduces some complaints, but recurring or persistent ones are not a matter to resolve alone: they require assessment by an appropriate specialist. This article describes working conditions; it does not replace a consultation and contains no treatment or exercise recommendations.

One terminological aside. The everyday phrase “vocal cords” is not an anatomical name - the correct term is vocal folds. Nor are they “cords” in any mechanical sense: sound arises from the interaction of breath, vibration of the folds and resonance in the vocal tract, so speaking of a load on the folds alone would oversimplify the whole mechanism.

What the research shows

The literature on teachers’ voices is extensive but uneven: alongside measurements taken during real lessons there are questionnaires, laboratory experiments and reviews of widely differing methodology. Below are six items arranged to show how broad this body of knowledge is, how vocal load is actually measured, and where the conclusions stop.

How broad the evidence is

Scoping review (Mealings, Maggs and Buchholz, 2024). An Australian team asked what is known about the relationship between classroom acoustic conditions and teachers’ health and wellbeing [1]. It was a scoping review - a study mapping the research field, not a meta-analysis combining results into a single figure. The authors analysed 33 articles. The area addressed most often was vocal health; wellbeing, fatigue and mental load were studied less. The most important thing for the reader is what the review shows about the findings themselves: they were not uniform. Some studies found negative associations between noise, class size or reverberation and the state of teachers’ voices; others found no significant effect; and the methods and definitions used differed enough to limit direct comparison. What this means for schools: the topic is real and well documented as a research field, but should not be presented as settled. Limitation: a scoping review does not assess effect size or resolve discrepancies between studies.

How vocal load is measured

Measurements during real lessons (Kristiansen et al., 2014). A Danish team examined how classroom acoustics and teachers’ noise exposure, vocal load and speaking time during lessons relate to the development of vocal and mental fatigue [2]. This was a field study: measurements were taken during real lessons, with 35 teachers. Noise exposure and speech parameters - including phonation time and voice level - were recorded, reverberation conditions were measured separately in the rooms, and vocal and mental fatigue were assessed over the working day. The authors analysed the links between teaching conditions and the build-up of both kinds of fatigue. What this means for schools: vocal load can be studied in real working conditions, not only through questionnaires; the room is one of the factors considered. Limitations: a group of 35 is small, and associations observed in such a design do not allow any single parameter to be identified as an independent cause of fatigue - speaking time, noise level and reverberation conditions change together. Detailed numerical values require verification in the full text of the publication, which is why we do not quote them here.

Four-day voice monitoring (Puglisi et al., 2017). An Italian team observed teachers’ voices at work over four days [3]. The study involved 27 female primary-school teachers, from whom 61 working-day samples were collected. It used voice-monitoring devices based on contact sensors attached at the neck - these record the vibrations that accompany phonation, so they measure speech parameters and are not a diagnostic tool: they do not identify disorders. Voice level, fundamental frequency and phonation time were analysed, comparing a short conversational task with actual teaching and relating the results to the rooms’ acoustic parameters. It followed that values obtained in a short conversation are not a simple equivalent of what happens during lessons, and that voice parameters were associated with the rooms’ acoustic conditions. What this means for schools: short recording samples are no substitute for observing a whole working day. Limitation: 27 participants from one type of school is too small and too homogeneous a group for the conclusions to be transferred to all teachers.

Measurement plus self-report (Cantor Cutiva and Burdorf, 2015). This study combined objective measurements of acoustic conditions in schools with teachers’ own reports about the state of their voices [4]. Distinguishing the two data sources is crucial here: measurement tells you what the room is like, self-report how the teacher perceives their own voice - two different layers of information that can diverge. The authors observed associations between acoustic conditions and reported voice complaints, though not all the factors analysed produced equally clear results. What this means for schools: it is worth collecting both kinds of data, because neither alone describes the problem. Limitation: the study design describes co-occurrence; it does not establish medical causation.

What the experiments show

Reading with a raised voice (Nusseck et al., 2022). A German team ran an experimental study: teachers read a text in a normal condition and with a raised voice, including in the presence of noise [5]. Voice parameters and perceived effort were measured. The results showed that speaking with a raised voice - especially in noise - changes vocal behaviour and increases perceived effort compared with unconstrained speech. What this means for schools: the difference between normal and raised speech is measurable, not merely felt. The limitations matter, though: a short reading task under controlled conditions does not reproduce a full lesson or a whole working day - it lacks movement, pupils’ responses, the interrupted rhythm of speech and the accumulation of load over many hours. Nor does the study show that raising the voice once leads to dysphonia.

Risk factors - and what remains unresolved

Systematic review with meta-analysis (Byeon, 2019). In our set this publication is the most important safeguard against a one-sided message [6]. The author analysed 16 publications on risk factors for voice disorders in teachers, considering both individual and occupational characteristics. Factors associated with higher risk included loud speaking and the number of lessons taught. At the same time, not all noise-related measures and self-reports proved statistically significant, and the author pointed to the need for longitudinal studies that would establish the direction of the associations. The conclusion is therefore restrained: noise and acoustic conditions appear in this literature as one of the factors considered, not as the sole cause of voice disorders - nor even as an established leading one.

When the teacher speaks louder - and so does the class

A possible sequence of events in an acoustically difficult room runs like this: the background level rises, the teacher raises their voice, pupils - in order to hear each other in conversation - also speak louder, the background rises further, and the teacher’s advantage over it improves less than the increase in their voice level would suggest. Speaking louder does not shorten reverberation time, so the clarity of the message need not improve in proportion to the effort.

Two caveats are needed here. First, this is not an inevitable spiral occurring in every lesson: how it unfolds depends on the room, the type of activity, the number of people and how the work is run. Second, describing the mechanism is not an attribution of blame - neither to pupils, who behave typically for their age and task, nor to the teacher, who responds reflexively in the way described earlier as the Lombard effect.

The problem cannot be reduced to speaking technique

Many factors affect the condition of the voice at once. They include: the intensity and total duration of voice use, the number of lessons taught, the nature of the activity (lecture, group work, physical education, sessions at a pool or in a workshop), respiratory infections, individual predisposition, general health, stress, the realistic opportunity to rest between lessons, the acoustic conditions of the rooms, and the organisation of work - from the timetable to the number of consecutive hours in the same room.

Voice training has its place in this set and can be valuable. The problem arises when it becomes an institution’s only answer to repeated reports. Teaching someone to speak better in conditions that make communication harder shifts the entire responsibility onto the employee and ignores what the school as an organisation can change. No technique eliminates reverberation in a room, and none guarantees that problems will not arise.

What the research does not allow us to say

This section matters as much as the previous ones. A large part of the literature discussed is observational: it describes the co-occurrence of conditions and complaints, not a causal chain. Some data come from teachers’ self-reports, which are valuable but are not clinical examinations. Individual studies use different definitions of a “voice problem” - from a single questionnaire item to a specialist’s assessment - which makes comparison harder.

The findings do not agree. The 2024 scoping review states plainly that some studies found negative associations and some did not [1]. Not all measurements of noise and reverberation lead to identical conclusions, and in the meta-analysis of risk factors not all noise-related measures proved statistically significant [6]. Laboratory experiments give control over conditions but do not reproduce a full working day [5]. Sample sizes in the field studies are small: 35 and 27 participants in the two works discussed [2][3].

Finally, two limits that are easy to forget. The state of the voice is affected by factors unrelated to acoustics - infections, teaching hours, stress, individual predisposition. And most importantly: no conclusion about an individual’s health can be drawn from population findings. None of the studies discussed here allows an assessment of any single teacher’s voice.

Summary

Let us return to the teacher from the start of this article, whose voice sounds different in the sixth lesson than in the first. The research does not allow us to say that the cause is solely the room’s acoustics - nor solely their way of speaking. It does allow something narrower and more useful: delivering the same message takes different amounts of effort in different rooms, and that effort accumulates over the working day. A tired voice at the end of the day can therefore be the result of a whole day of communicating in conditions that constantly raise the cost of being heard.

Caring for a teacher’s voice should not be limited to teaching them how to speak. It should also include asking in what conditions they have to be heard. The first is a matter of competence; the second is a matter of rooms, timetables and the organisation of work, and therefore the responsibility of the school as an institution. We wrote about why acoustic conditions at school are a public-health issue, not merely a matter of comfort, in the article on the health significance of noise at school.

References

1. Mealings K.T., Maggs L., Buchholz J.M., The Effects of Classroom Acoustic Conditions on Teachers' Health and Well-Being: A Scoping Review, „Journal of Speech, Language, and Hearing Research” 2024; 67(1): 346-367. DOI: 10.1044/2023_JSLHR-23-00256; PMID: 38085689.
2. Kristiansen J., Lund S.P., Persson R., Christensen K.B., Shibuya H., Nielsen P.M., A Study of Classroom Acoustics and School Teachers' Noise Exposure, Voice Load and Speaking Time During Teaching, and the Effects on Vocal and Mental Fatigue Development, „International Archives of Occupational and Environmental Health” 2014; 87(8): 851-860. DOI: 10.1007/s00420-014-0927-8; PMID: 24464557.
3. Puglisi G.E., Astolfi A., Cantor Cutiva L.C., Carullo A., Four-Day-Follow-Up Study on the Voice Monitoring of Primary School Teachers: Relationships With Conversational Task and Classroom Acoustics, „The Journal of the Acoustical Society of America” 2017; 141(1): 441-452. DOI: 10.1121/1.4973805; PMID: 28147558.
4. Cantor Cutiva L.C., Burdorf A., Effects of Noise and Acoustics in Schools on Vocal Health in Teachers, „Noise & Health” 2015; 17(74): 17-22. DOI: 10.4103/1463-1741.149569; PMID: 25599754.
5. Nusseck M., Immerz A., Richter B., Traser L., Vocal Behavior of Teachers Reading With Raised Voice in a Noisy Environment, „International Journal of Environmental Research and Public Health” 2022; 19(15): 8929. DOI: 10.3390/ijerph19158929; PMID: 35897294.
6. Byeon H., The Risk Factors Related to Voice Disorder in Teachers: A Systematic Review and Meta-Analysis, „International Journal of Environmental Research and Public Health” 2019; 16(19): 3675. DOI: 10.3390/ijerph16193675; PMID: 31574928.
7. Schiller I.S., Remacle A., Durieux N., Morsomme D., Effects of Noise and a Speaker's Impaired Voice Quality on Spoken Language Processing in School-Aged Children: A Systematic Review and Meta-Analysis, „Journal of Speech, Language, and Hearing Research” 2022. DOI: 10.1044/2021_JSLHR-21-00183; PMID: 34902257.

This article is for information only. It does not replace an acoustic measurement, an assessment of working conditions or a medical consultation about the voice.