The same classroom, a different effort. Why a child’s age matters for listening in noise

In the back row an adult observer and a seven-year-old pupil sit side by side. The teacher speaks the same sentence to the whole room. In the background someone drags a chair, two people finish a whispered conversation, and the room has noticeable reverberation. The adult reconstructs the message without difficulty and notes that audibility is good. Does it follow that the task was equally easy for the child sitting half a metre away? In other words: does “hearing” mean exactly the same task for a child and an adult?

“Their hearing is fine” - but what are we actually testing?

In conversations about schools the single word “hears” conceals several different things. Separating them is what reveals how an adult’s task differs from a seven-year-old’s.

• Hearing sensitivity - whether a person detects a quiet sound. This is the question an audiometric test answers.
• Speech recognition - whether they can correctly identify the words or sentences they hear.
• Speech recognition in noise - whether they can extract the message that matters from competing sounds.
• Comprehension - whether they give the message meaning rather than just repeating words.
• Following an instruction - whether they retain the information and can act on it.
• Listening effort - how much resource completing the task successfully required.

Hence a sentence worth remembering: hearing a simple tone normally in quiet and successfully following a teacher in a noisy classroom are two different tasks. This does not undermine the value of audiometric testing - it simply answers a different question from the one a school is asking.

In good conditions the differences are smaller

When the message is clear, the speaker close, the surroundings calm, no competing speech present and reverberation slight, a large share of the acoustic information reaches the listener. The task is then mainly one of reception.

When the signal degrades - through noise, reverberation, distance or other voices - the listener has to draw more often on resources that have nothing to do with the ear: knowledge of the language, vocabulary, predicting the next word, the context of the topic, attention, memory and ordinary communicative experience. An older pupil and an adult usually have more of these than a child just starting school. That does not mean an adult always scores better, or that the gap is constant - it depends on how hard the conditions are and what the task is.

A question almost half a century old

Sentence recognition in noise in children aged 9-17 (Elliott, 1979). As early as the 1970s it was noticed that the use of speech in noise changes throughout the school years [1]. The study used a sentence-recognition-in-noise test in which sentences differed in linguistic predictability - in some the final word could be inferred from context, in others it could not.

Nine-year-olds scored lower than eleven-year-olds, and the eleven- and thirteen-year-old groups did worse than the fifteen- and seventeen-year-olds under the conditions analysed. A significant part of these differences concerned highly predictable sentences at a particular signal-to-noise ratio - precisely the situations in which one has to be able to use context. It does not follow that “adult hearing is reached at fifteen”; the study set no developmental boundary. What does follow is different: the ability to use speech in noise continues developing through the school years.

A first-grader, a third-grader and an adult in one room

Noise and reverberation in classroom-like conditions (Klatte, Lachmann and Meis, 2010). This is one of the most important studies for our topic, because it compares three groups in the same set-up: first-grade children, third-grade children and adults [2]. Both speech recognition and the execution of spoken instructions were tested, with typical classroom noise and with background speech, under conditions of differing reverberation time (the experiment simulated values of about 0.47 s and about 1.1 s - these are study parameters, not standards for Polish classrooms).

Three findings matter here. Children proved more susceptible to background sounds than adults. On the instruction-comprehension task the disruption was greater for first-graders than for third-graders. And finally: competing speech affected not only sound recognition but also the more complex processing of the message. This is not evidence that children “can’t concentrate” - it is information that, with the same signal, the task was harder for them.

Noise and reverberation together

The combined effect of noise and reverberation (Neuman, Wróblewski, Hajicek and Rubinstein, 2010). This study compared children aged 6-12 and young adults with normal hearing across various combinations of noise, reverberation and signal-to-noise ratio [3]. The reverberation conditions covered values of about 0.3 s, 0.6 s and 0.8 s - again, experimental parameters, not design requirements.

The overall sense of the results is simple and practical: the harder the conditions became, the more pronounced the differences between younger children, older children and adults could be. Conditions good for everyone differentiate little; hard conditions differentiate a great deal. The exact number of participants needs confirming in the primary publication, which is why we do not quote it, and no universal requirement for signal-to-noise ratio or reverberation time in schools can be derived from a single experiment.

Four age groups and momentary gaps in the noise

Steady and modulated noise (Wróblewski, Lewis, Valente and Stelmachowicz, 2012). The study involved 48 children in four age groups - 7-8, 9-10, 11-12 and 13-14 - and 12 young adults aged 23-30, twelve people per group [4]. Speech recognition was compared in steady and modulated noise, with and without reverberation, at various simulated distances within a room.

A phenomenon worth explaining in plain terms comes in here. When the noise level briefly drops - because noise is not even but pulsing - the listener can exploit those short moments in which fragments of speech become easier to catch. The literature calls this masking release. Reverberation works against it, because sound reflections partly “fill in” those momentary gaps. The study showed that the ability to use such glimpses develops with age. It is not a single, discrete neurological skill but the product of several developing processes working together.

A four-year-old, a twelve-year-old and an adult

Speech recognition in steady and interrupted noise (Koopmans, Goverts and Smits, 2018). One experiment in this work involved 112 children with normal hearing aged 4-12 and 33 adults [5]. The task was to recognise digit sequences in steady and in interrupted noise under various listening conditions. Performance improved with age.

The nuance is the most interesting part. In steady noise, the scores of children aged about 10-12 approached those of adults. In interrupted noise, developmental differences remained visible for longer. Hence a conclusion worth repeating in discussions about school design: there is no single moment at which “adult listening” is achieved. When a child approaches adult performance depends on the type of task and the type of interference - so the sentence “a child reaches adult hearing at twelve” is simply untrue.

Why conversation disturbs differently from a hum

Type of interference and age (Johnstone and Litovsky, 2006). This study compared children aged 5-7 with adults, analysing different types of competing sound and the spatial separation of sources [6]. It introduces a distinction useful in any discussion of school acoustics.

Energetic masking occurs when competing signals overlap acoustically and part of the speech is simply covered. Informational masking arises when the interference itself carries meaningful information - intelligible conversation, for instance - and makes it harder to direct attention to the right source. In real situations the two mechanisms often occur together and are not entirely separable.

Translated to the classroom: the hum of ventilation and two pupils talking can have a similar sound level and still not be equally easy to ignore. Competing speech can be a particularly demanding form of interference, especially for younger pupils.

“He heard it” does not always mean “he learned it”

Recognition versus learning in a simulated classroom (Valente, Plevinsky, Franco, Heinrichs-Graham and Lewis, 2012). The study involved 50 children with normal hearing aged 8-12, and the conditions covered various combinations of signal-to-noise ratio and reverberation time in a simulated classroom [7]. The result is instructive: on simple sentence-recognition tests the children scored very highly, whereas the more demanding tasks of comprehending and learning material proved more sensitive to poorer acoustic conditions - especially in the younger participants.

Hence a distinction that organises the whole discussion: recognising speech, understanding a lesson and remembering the material are three different things, and the first is the easiest to manage. A test in which a child repeats sentences can therefore show a near-maximum score under conditions in which learning a new topic would already be markedly harder. We write more fully about the cognitive costs of listening in noise in the article on attention, memory and cognitive effort.

A classroom instruction is not a single word

Understanding instructions in noise and reverberation (Lewis, Manninen, Valente and Smith, 2014). The study covered children aged 8-12 with normal hearing carrying out complex instructions under several conditions: in noise, in noise combined with reverberation, with one talker, with multiple talkers, and with multiple talkers plus competing commentary [8]. Performance was generally worse where noise combined with reverberation, and the situations with additional competing speech proved the hardest.

That describes a pupil’s real task well. A typical classroom instruction requires listening to the whole utterance, holding its elements in memory, identifying the right speaker, ignoring messages not addressed to you and carrying out several actions in the right order. Repeating a single word is an incomparably easier task by comparison.

Why “children have better hearing” is too simple a sentence

A young child with normal hearing can have very good hearing sensitivity - better than an adult’s. That does not, however, mean adult-level performance on every speech task in difficult conditions, because understanding a lesson requires all at once: catching the voice, separating it from competing sources, recognising the words, using context, sustaining attention, linking successive parts of the utterance, holding some information in memory, understanding the message and applying it. This is a functional simplification for the reader, not a description of nine separate modules in the brain.

Age-related differences therefore have no single cause. They result from the interplay of many developing abilities: language experience, vocabulary, the ability to use context, selective attention, memory, cognitive control, communicative experience, spatially separating sound sources and exploiting momentary gaps in interference. The explanation “a child’s brain is simply immature” is far too much of a shortcut - and it tells a designer or a teacher nothing.

How listening changes over the years

The description below is deliberately not a table of ages with grades. There is no single reliable boundary common to all tasks and all types of interference.

• The start of school. Differences from adults are often clearly visible in demanding listening conditions - with reverberation, competing speech and greater distance [2].
• The middle primary years. On some simpler tasks performance approaches adult levels, but not with every type of interference [5].
• Older children and teenagers. Further development depends on the particular function and type of task; it does not end at one moment [1] [4].
• Adults. Adult level does not mean immunity to noise. Unfavourable conditions still impair comprehension and increase listening effort.

Distance from the speaker matters

With distance from the teacher, the direct speech signal becomes less favourable relative to background sounds, reflections from the room’s surfaces and other sources. For a pupil with fewer linguistic resources to fill the gaps, that change is felt more keenly.

This does not, however, lead to the recommendation that “all younger children should sit at the front”. If particular places in a room give markedly worse access to speech, the basic problem is the environment, not one child’s seat - moving pupils solves one person’s situation and leaves the room as it was. We describe the conditions in which good speech intelligibility arises in the article on reverberation and speech clarity.

Do the youngest need better conditions?

Research showing that younger children’s performance depends more strongly on listening conditions is an argument for taking particular care over the acoustics of spaces intended for the youngest pupils - early-years classrooms, after-school rooms and the spaces where children spend the most time.

It does not mean older children are immune, or that acoustics do not bother adults. Nor does it mean that a single binding value for reverberation time or signal-to-noise ratio can be derived from one experiment. In Poland the requirements for school rooms are set by the relevant standards, and verifying them requires measurement - we write about this in the article on what an acoustic survey of a school actually measures. The developmental perspective does not replace measurement; it shows for whom the margin is smallest.

Listening in noise has been studied for decades

• 1979 - Elliott. Children and young people aged 9-17, sentence recognition in noise at differing levels of linguistic predictability [1].
• 2006 - Johnstone and Litovsky. Children aged 5-7 and adults, different types of masking and spatial separation of sources [6].
• 2010 - Klatte, Lachmann and Meis. First- and third-graders and adults in classroom-like conditions [2].
• 2010 - Neuman and colleagues. Children aged 6-12 and adults across combinations of noise and reverberation [3].
• 2012 - Wróblewski and colleagues. Children aged 7-14 in four groups, plus young adults [4].
• 2018 - Koopmans, Goverts and Smits. Children aged 4-12 and adults, steady and interrupted noise [5].

Broader context comes from the syntheses. A systematic review with meta-analysis on the effects of noise and reduced speaker voice quality on language processing in school-age children shows that the effects depend on the level of processing, age and type of task [9]. It is not, however, evidence of one effect identical for every child - a meta-analysis describes tendencies across a body of studies. Likewise, a literature review on speech intelligibility and classroom acoustics in primary schools organises the field but provides no single universal target value [10].

What the research does not allow us to say

There are plenty of limitations and they are worth stating plainly. Many of the experiments described were run in simulated conditions, and a short laboratory task does not reproduce a whole school day. Individual studies used different types of interference - steady noise, modulated noise, background speech - and the results are not directly comparable between them. The studies were conducted in different languages, which can itself affect results, since they depend on participants’ vocabulary and language experience. Some involved relatively small groups.

Interpretive limitations come on top. Good performance on a simple test does not mean it cost the same effort [7]. A group result describes a tendency, not an individual child’s capacity. The reverberation times and signal-to-noise ratios used in the experiments are study parameters, not requirements for schools [2] [3]. And something that should not be hidden, because it strengthens the credibility of the whole picture: in some easier conditions older children reach scores close to adults’ [5] - so the problem is not age as such, but the combination of age with the difficulty of the environment. How to set such tendencies against the real accessibility of lessons for particular pupils is described in the article on acoustics as a question of educational accessibility.

Summary

Let us return, finally, to the back row where an adult and a seven-year-old sit side by side. The teacher speaks the same sentence, in the same room, with the same noise and the same reverberation. The conditions are physically identical, but the task need not be equally easy - because the second listener has less language experience, less practice in picking out the right voice and fewer resources for filling in what the noise took away.

In designing a school environment, then, it is not enough to check whether an adult can understand the teacher. It is worth asking whether the signal is legible enough for the pupil who is still developing the ability to listen effectively in a complex environment.

References

1. Elliott L.L., Performance of Children Aged 9 to 17 Years on a Test of Speech Intelligibility in Noise Using Sentence Material With Controlled Word Predictability, „The Journal of the Acoustical Society of America” 1979; 66(3): 651-653. DOI: 10.1121/1.383691; PMID: 489836.
2. Klatte M., Lachmann T., Meis M., Effects of Noise and Reverberation on Speech Perception and Listening Comprehension of Children and Adults in a Classroom-Like Setting, „Noise & Health” 2010; 12(49): 270-282. DOI: 10.4103/1463-1741.70506; PMID: 20871182.
3. Neuman A.C., Wróblewski M., Hajicek J., Rubinstein A., Combined Effects of Noise and Reverberation on Speech Recognition Performance of Normal-Hearing Children and Adults, „Ear and Hearing” 2010; 31(3): 336-344. DOI: 10.1097/AUD.0b013e3181d3d514; PMID: 20215967.
4. Wróblewski M., Lewis D.E., Valente D.L., Stelmachowicz P.G., Effects of Reverberation on Speech Recognition in Stationary and Modulated Noise by School-Aged Children and Young Adults, „Ear and Hearing” 2012; 33(6): 731-744. DOI: 10.1097/AUD.0b013e31825aecad; PMID: 22732772.
5. Koopmans W.J.A., Goverts S.T., Smits C., Speech Recognition Abilities in Normal-Hearing Children 4 to 12 Years of Age in Stationary and Interrupted Noise, „Ear and Hearing” 2018; 39(6): 1091-1103. DOI: 10.1097/AUD.0000000000000569; PMID: 29554035; PMCID: PMC7664447.
6. Johnstone P.M., Litovsky R.Y., Effect of Masker Type and Age on Speech Intelligibility and Spatial Release From Masking in Children and Adults, „The Journal of the Acoustical Society of America” 2006; 120(4): 2177-2189. DOI: 10.1121/1.2225416; PMID: 17069314.
7. Valente D.L., Plevinsky H.M., Franco J.M., Heinrichs-Graham E.C., Lewis D.E., Experimental Investigation of the Effects of the Acoustical Conditions in a Simulated Classroom on Speech Recognition and Learning in Children, „The Journal of the Acoustical Society of America” 2012; 131(1): 232-246. DOI: 10.1121/1.3662059; PMID: 22280587.
8. Lewis D.E., Manninen C.M., Valente D.L., Smith N.A., Children's Understanding of Instructions Presented in Noise and Reverberation, „American Journal of Audiology” 2014; 23(3): 326-336. DOI: 10.1044/2014_AJA-14-0020; PMID: 25036922; PMCID: PMC4154970.
9. 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; 65(1): 169-199. DOI: 10.1044/2021_JSLHR-21-00183; PMID: 34902257.
10. Murgia S. i wsp., Systematic Review of Literature on Speech Intelligibility and Classroom Acoustics in Elementary Schools, „Language, Speech, and Hearing Services in Schools” 2023. DOI: 10.1044/2022_LSHSS-21-00181; PMID: 36260411.

This article is for information only. The findings described concern tendencies observed in research and do not allow an assessment of any individual pupil.