---
title: "Synchronous classifier for an isolated French fricative recording (6 classes: f, s, v, z, ʃ, ʒ), built for the Aphasi…"
method: POST
path: "/api/classify-french-fricative"
tags: ["Phoneme & Classification"]
---

# Synchronous classifier for an isolated French fricative recording (6 classes: f, s, v, z, ʃ, ʒ), built for the Aphasi…

`POST /api/classify-french-fricative`

## Request

- Base URL: `https://platform.vocametrix.com`
- URL: `https://platform.vocametrix.com/api/classify-french-fricative`
- Auth: API key in header `X-API-Key`

## Request body

- object
  - `audio` string, required: Mode 1 (use ONE of audio/blobUrl/fileId). Direct audio file upload, multipart/form-data — the field name MUST be exactly `audio`.
  - `blobUrl` string, required: Mode 2 (use ONE of audio/blobUrl/fileId), JSON body. HTTPS URL of the audio file, downloaded server-side.
  - `fileId` string, required: Mode 3 (use ONE of audio/blobUrl/fileId), JSON body. fileId from a prior /api/assignFileId upload.
  - `expected_fricative` string: Optional (also accepted as expectedFricative, any input mode). When provided, the response is scored against this fricative.

## Response `200`

Successful response

- object
  - `success` boolean: Boolean — true if the classification succeeded.
  - `predicted_fricative` string: Predicted fricative (IPA).
  - `confidence` string: Confidence for the predicted fricative (0.0 - 1.0).
  - `all_probabilities` object: Object of probabilities for all 6 fricatives.
  - `audio_duration` number: Audio duration in seconds.
  - `processing_time_seconds` number: Server-side processing time in seconds.
  - `model_name` string: Model used, e.g. "fricative-aphasix-champion".
  - `expected_fricative (conditional)` string: Echoed back only when expected_fricative/expectedFricative was provided in the request.
  - `is_correct (conditional)` boolean: Boolean — true when predicted_fricative matches expected_fricative.
  - `expected_fricative_probability (conditional)` string: The model's probability for expected_fricative, from all_probabilities.
  - `score (conditional)` integer: expected_fricative_probability rounded to a 0-100 integer.

## Other responses

- `400`: Bad request — missing or invalid parameter
- `401`: Unauthorized — missing or invalid API key
- `429`: Rate limit exceeded
- `500`: Server error

---

[API](https://skmtc.dev/vocametrix/apis/vocametrix-api.md) · [All operations](https://skmtc.dev/vocametrix/apis/vocametrix-api/llms.txt) · [OpenAPI document](https://skmtc.dev/vocametrix/apis/vocametrix-api/revisions/8a54d01bcc81?raw)