Speech Sound Patterns in Bilingual Children

New to this topic? Start with our companion article: Bilingual Children and Speech Sounds: What's Typical | Brisbane Speech Pathologist

Your child swaps sounds between languages. They pronounce words differently from their classmates. They're harder to understand in one language than the others. Which of these matters — and which is just the normal business of learning two or more sound systems at once?

This article is the decision-making companion to our overview of typical bilingual speech sound development. Where that piece explains how bilingual phonology develops, this one zooms in on specific patterns and helps you sort "keep an eye on it" from "book an assessment." What looks like an error in English is often a perfectly logical transfer from another language's sound system — and the detective work starts with knowing which language is contributing what.

A Quick Recap of Typical Patterns

Before we look at concerning patterns, a brief reminder of what's expected in bilingual and multilingual children's speech — we cover this in detail in the companion article:

Accent Influence

Different rhythm, stress, or vowel qualities carried from one language into another. This is an accent, not a speech disorder, and does not need treatment.

Transfer Patterns

Transfer happens when your child applies the rules of one language to another. Common examples:

Substituting sounds. If your child's home language doesn't include the English "th" sound, they might say "dis" instead of "this" or "fink" instead of "think." This is because they're using the closest sound from their home language.
Changing vowels. Vowel systems vary enormously between languages. Your child might produce English vowels with qualities from their home language, making some words sound a bit different.
Simplifying consonant clusters. Some languages don't allow two or three consonants to sit next to each other the way English does (think "str-" in "street" or "-nds" in "friends"). A child whose home language has simpler syllable structures might reduce these clusters — saying "seet" for "street" — which is a transfer pattern, not an error.
Adding or dropping sounds at the ends of words. Languages differ in whether words can end with consonants. If your child's home language typically ends words with vowels, they might leave off final consonants in English.

Dominance Effects

Children are typically clearer and more accurate in their dominant language — the one they use and hear most. If they've recently started school and are getting much more English input than before, their English speech may improve rapidly while their home language speech stays the same or even seems to go backwards slightly. This is a normal shift in language balance, not a sign of a problem.

Variation and Inconsistency

Bilingual children may produce the same word differently on different occasions — sometimes with a sound from one language, sometimes with a sound from the other. This inconsistency can look concerning, but it often reflects the child's active process of working out which sounds belong to which language.

Patterns That Might Indicate a Speech Sound Difficulty

While the patterns above are typical, some features of a child's speech might suggest something more is going on. The most important principle is this: a true speech sound difficulty will show up across all of a child's languages, not just one — whether a child speaks two, three, or more.

A few broad patterns tend to catch a speech pathologist's attention:

Errors that don't fit either language

If your child is making sound errors that can't be explained by the rules of either language, or by transfer between them, that's worth a closer look. For example, consistently leaving out sounds in positions where both languages require them, or substituting sounds in ways that don't match either system, doesn't fit the usual bilingual patterns. A very limited range of consonants across both languages — relying on just a handful of sounds like "d," "b," and "m" — can also point to a phonological difficulty rather than a transfer effect.

Low intelligibility in both languages

If your child is hard to understand for familiar listeners in both languages — not just in English, and not just for strangers — that's a meaningful sign. In my experience, when grandparents or relatives who speak the home language say they're also struggling to understand the child, that's usually the moment I know we're looking at something beyond typical bilingual transfer. By around age 4, most children should be understood most of the time by unfamiliar listeners.

Not improving over time

All children's speech becomes clearer as they grow. If your child's speech doesn't seem to be progressing in either language — if they're still making the same errors a year on, despite plenty of input — that suggests they may need some support.

How to Tell the Difference

Figuring out whether a pattern is a bilingual difference or a genuine speech sound difficulty is the kind of detective work that needs a speech pathologist who understands bilingual phonology. It's not something that can usually be worked out from the outside.

Broadly, a good bilingual speech sound assessment starts with a careful language history — which languages your child hears and speaks, how much, from whom, and in what contexts — and gathers information about speech in every language your child uses, with support from interpreters or knowledgeable family members where needed. From there, the clinician's job is to work out whether the errors can be explained by cross-linguistic transfer (typical) or reflect patterns that are unusual in both languages (potentially a difficulty). Fabiano-Smith and Goldstein (2010) demonstrated that bilingual children's phonological systems interact in predictable ways, and that clinicians who understand these interactions make more accurate diagnostic decisions. This is genuinely specialist work, and it's where a speech pathology assessment earns its keep.

Ears first, then patterns. When untangling speech sound patterns in a bilingual child, it's important to know what they're actually hearing in both languages. A paediatric audiologist can check that in a single visit, and it saves a lot of guesswork later.

When to Seek Help

If you're unsure, here's a simple guide:

Likely typical patterns — keep an eye on progress: Your child has an accent, uses transfer patterns from their home language, or is clearer in one language than the other. They're making progress over time and can generally get their message across. If you ever feel uncertain, an assessment can give you peace of mind.
Worth checking — book an assessment: Your child is difficult to understand in both languages, doesn't seem to be improving, or you (or family members who speak the home language) are concerned. Errors don't seem to match the patterns of either language.
Seek support soon: Your child is very difficult to understand in both languages, is becoming frustrated by not being understood, or has error patterns that seem unusual or are getting worse.

A note on "waiting": Even when patterns look typical, "wait and see" isn't usually our advice. If something doesn't feel right, a speech pathology assessment is one common approach to know for sure. There's no harm in checking — and if everything is on track, you'll walk away reassured.