Whistling S Sound: Why an S Whistles and What Helps

What a whistling S is

A whistling S, which phoneticians call a whistled fricative, has a clear tone riding on top of the ordinary hiss of S. It is perhaps most common on S, but Z and “sh” can whistle too.³

The explanation proposed in phonetics research is an edge tone. The tongue shapes a thin jet of air, and the edge of the front teeth is what that jet strikes, much like air across a flute. On this model the lips are not needed to make the whistle, although rounding them lowers its pitch.¹

On a recording, an ordinary S shows up as a broad band of noise, while the whistle appears as a sharp, narrow peak. In one Australian study, researchers identified a whistled S by an audible whistle together with a strong band of energy on the spectrogram.^1,3

A slight whistle is common. The same Australian study, which recorded adults aged 18 to 40 and 15 children aged 4 to 5 with no history of speech disorder, found whistled S “relatively common” in both groups. The proportion was higher in children than in adults, and higher in women than in men, but there were too few whistled sounds to test those differences statistically. That comes from a single conference paper, so the pattern may not hold everywhere.³

English tends to treat a whistle as a feature of disordered speech, yet unwanted whistles are widely reported among American English speakers. In some Southern Bantu languages, including Shona and Changana, a whistled S is a separate speech sound that changes the meaning of a word.^1,2

What makes an S whistle

The tongue groove and the air jet

On the edge-tone model, the tone comes from the thin jet of air leaving the tongue and meeting the edge of the teeth. That means the shape of that jet matters.¹

Classic denture-fitting teaching says that a tongue groove that is too deep can produce a whistle on S. That teaching comes from a dental school handout, so treat it as low-grade evidence.⁷

Where the front teeth sit

The teeth are the edge the air strikes, so their position matters too. In denture experiments, changing the angle of the upper front teeth changed how S sounded. Denture teaching adds that lower front teeth set too far forward can also produce a whistle.^1,4,5,7

Gaps between the teeth: plausible, not proven

Could a gap between the front teeth cause a whistle? The edge-tone model, in which the front teeth are the edge the air strikes, makes that plausible. We found no peer-reviewed study that directly links tooth gaps to a whistling S, though, so treat the idea as unconfirmed.¹

Dentures and braces: widely reported, less well tested

Dentures and braces are often said to cause whistling, but the evidence is thinner than it sounds. One linguist's account of the link relied partly on a newspaper report. The controlled studies measured distortion of S in general, not whistling specifically.^1,4,6

How people whistle on S on purpose

Going by the edge-tone model, a raised tongue tip sends a thin, flat jet of air at the front teeth to produce the tone, and rounding the lips lowers its pitch. Speakers of Shona and of Changana (also called Tsonga) make this sound deliberately as part of their language. For a child working on a clear S, though, the goal is a smooth hiss, not a whistle.^1,2

How a whistling S differs from the lisp types

A whistling S is usually not counted among the four lisp types. ASHA lists distortions as one kind of speech sound error. Clinical phonetic transcription (the extIPA symbols for disordered speech) also has its own mark for a whistled sound, so a whistle can be recorded in its own right.^14,8,1

The key listening difference is this: a whistle sits on top of an S that still sounds like S. A frontal lisp pulls S toward “th,” and a lateral lisp makes it sound wet.^3,10,14

• Lisp in Children: all four lisp types at a glance
• Dentalized Lisp: the muffled S made against the back of the teeth

Dentures, braces and retainers

New dentures or front-tooth work

Speech changes after new dental restorations are common. Most are temporary, although they still worry many patients.⁴

In one experiment with duplicate dentures, tilting the upper front teeth away from their original angle usually made S worse, whichever way they were tilted. Tilting them outward had the larger effect.⁴

A second study by the same team, with 18 denture wearers, found that the position of the upper front teeth affected S straight away. The authors recommended placing denture teeth in the original tooth position as accurately as possible. They also concluded that the wearer's nerve and muscle responses mattered more than the change in airflow for the first distortions.⁵

Braces, retainers and palatal expanders

A 2018 systematic review of 13 studies and 297 patients found that fixed braces, retainers and palatal expanders can all affect how clear speech is. S was among the sounds most affected. Lingual braces (fitted behind the teeth), palatal expanders and Hawley retainers had the clearest effect.⁶

Most speech changes returned to normal within weeks, but S distortion could last more than 3 months. The review rated its evidence as low quality. It also looked at S distortion in general rather than at whistling in particular.⁶

• If a whistle started with dentures or front-tooth work and hasn't settled as you adjust, tell your dentist. Tooth position and denture shape are theirs to adjust.
• If it started with braces, a retainer or an expander, ask the orthodontist first.
• Please don't file, bend or reshape a denture or retainer yourself.
• If the whistle had nothing to do with dental work, or it outlasts the adjustment period, a speech-language pathologist is the right person to listen.

• Lisp with Braces: how appliances change S, and what helps

Just a variation, or worth an assessment?

We found no research that sets a point at which a whistle becomes a problem. A slight, occasional whistle on an otherwise clear S fits what researchers hear in typical speech: in the Australian study, 62% of speakers produced at least one whistled S, and about 1 in 10 of all the S sounds recorded had a whistle.^3,1

ASHA notes that speech differences that come from a dialect, or from another language a person speaks, do not indicate a speech sound disorder. A speech assessment also includes an oral mechanism exam, which looks at how the teeth meet and at any specific tooth differences.⁸

Young children

S is a late and variable sound. In one well-known chart described in a major U.S. review, S had the widest age range of acquisition of any consonant, and studies disagree on its timing. For that reason this page does not give a single “should have S by” age.⁹

A “th”-like S is common in preschoolers, and NHS guidance lists “s as th” at ages 3 to 5 as a typical error that is not a cause for concern. A slight whistle in a child whose S is otherwise clear fits the finding that whistled S turns up in typical Australian 4- and 5-year-olds' speech, in a higher proportion than in adults' speech.^10,13,3

A wet, slushy S is different, because a lateral lisp is not part of typical development.¹⁰

School-age children, teens and adults

ASHA's Practice Portal cites estimates that 3.6% of 8-year-olds have a persistent speech sound disorder and that 1%–2% of young adults have residual speech errors. Not every distorted S settles on its own.⁸

Practice that changes the airflow

We found no outcome research on treating a whistled S. The ideas below are low-risk experiments based on how the whistle is made, not proven methods. The tone comes from a thin jet of air striking the front teeth, so the aim of practice is to change that jet.¹

NHS speech and language therapy advice starts with listening: helping a child hear the difference between a clear S and the sound they make. It also suggests practicing S on its own before moving it into words.¹²

1. 1Record yourself saying “see, sun, bus, soup, glasses” and play it back. Do you hear a whistle on a clear S, a “th” sound, or a wet, slushy S? This is for listening, not self-diagnosis.
2. 2In front of a mirror, say a long “sss” using a little less air.
3. 3Try the tongue tip a touch further back from the teeth.
4. 4Try the jaw very slightly lower, by a millimeter or two.
5. 5Keep whichever version sounds like a smooth, even “sss.” Once that comes easily, try it at the start of short words like “see” and “sun.”
6. 6Keep sessions short and positive, and stop if they become frustrating.

In one phonetics paper, the two speech-language pathologists the author consulted did not suggest changing lip position to treat a whistle. That fits the edge-tone model, in which the lips change the pitch of the whistle rather than whether it happens.¹

Helping a child

NHS advice for children is to model the word back clearly (“You want the blue sock?”) and to avoid putting too much pressure on them. One leaflet also notes there is no need to work on a lisp that isn't causing a difficulty.^10,11

For a quick first look at a child's S and Z, our free lisp check below listens to a few words. It is a preliminary screen for ages 4 and up, not a test result. It does not name a lisp type, and it is not designed to tell a whistle apart from a lisp. That takes a speech-language pathologist.

• The S Sound: tongue position and practice words for a clear S

Frequently asked questions

References

14 sources from authoritative bodies. Last reviewed October 2026.

1. 1.UC Berkeley Phonology LabShosted — Just put your lips together and blow? The whistled fricatives of Southern Bantu — Conference paper (phonetics, ISSP), 2006.
2. 2.Cascadilla Proceedings Project (LingRef)Shosted — Articulatory and acoustic characteristics of whistled fricatives in Changana — Conference paper (Selected Proceedings of ACAL 40), 2011.
3. 3.Peer-reviewedTobin, Penney, White & Cox — Give a little whistle: a neglected characteristic of Australian English productions of /s/ — Peer-reviewed conference paper (SST 2024), 2024.
4. 4.Peer-reviewedRunte et al. — The influence of maxillary central incisor position in complete dentures on /s/ sound production — Experimental study (Journal of Prosthetic Dentistry), 2001.
5. 5.Peer-reviewedRunte et al. — Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors — Experimental study (n = 18), 2002.
6. 6.Peer-reviewedChen, Wan & You — Speech and orthodontic appliances: a systematic literature review — Systematic review, 2018.
7. 7.Priyadarshini Dental College and Hospital, Department of ProsthodonticsHalder — Speech consideration in complete denture — Educational handout (low-grade evidence), 2024.
8. 8.ASHASpeech Sound Disorders: Articulation and Phonology — Practice Portal page, 2026.
9. 9.Peer-reviewedCrowe & McLeod — Children's English Consonant Acquisition in the United States: A Review — Review, 2020.
10. 10.GovernmentLisps — NHS patient leaflet (Early Years SLT), 2026.
11. 11.GovernmentLisp Advice Leaflet — NHS patient leaflet (Children's SLT), 2019.
12. 12.GovernmentProducing /s/ – 'lisp' advice — NHS patient leaflet, 2025.
13. 13.GovernmentTypical patterns of speech sounds in young children — NHS patient resource, 2024.
14. 14.EBSCOSecrest — Lisping — Reference encyclopedia entry (Research Starters), 2024.