---
title: "Calculate S/Z ratio with age-specific interpretation and quality assessment"
method: GET
path: "/api/calculate-sz-ratio"
tags: ["Advanced Voice Analysis"]
---

# Calculate S/Z ratio with age-specific interpretation and quality assessment

`GET /api/calculate-sz-ratio`

## Request

- Base URL: `https://platform.vocametrix.com`
- URL: `https://platform.vocametrix.com/api/calculate-sz-ratio`
- Auth: API key in header `X-API-Key`

## Query parameters

- `sFileId` string, required
- `zFileId` string, required
- `patientAge` number, required
- `gender` string, required
- `clinicalContext` string
- `silenceThreshold` number
- `minVoicedDuration` number
- `minVoicelessDuration` number
- `edgePadding` number
- `maxRecordingDuration` number
- `chunkDuration` number
- `version` string

## Response `200`

Successful response

- object
  - `S_PHONATION_TIME` number: Total sustained /s/ phonation duration in seconds. Example: 18.7
  - `Z_PHONATION_TIME` number: Total sustained /z/ phonation duration in seconds. Example: 19.2
  - `SZ_RATIO` number: S/Z phonation time ratio (primary clinical measure). Example: 0.97
  - `S_EFFICIENCY` number: Percentage of /s/ recording with actual phonation. Example: 85.4
  - `Z_EFFICIENCY` number: Percentage of /z/ recording with actual phonation. Example: 87.2
  - `S_PHONATION_SEGMENTS` number: Number of continuous /s/ phonation segments. Example: 3
  - `Z_PHONATION_SEGMENTS` number: Number of continuous /z/ phonation segments. Example: 2
  - `S_LONGEST_SEGMENT` number: /s/ longest continuous segment duration in seconds. Example: 12.5
  - `Z_LONGEST_SEGMENT` number: /z/ longest continuous segment duration in seconds. Example: 15.8
  - `MEAN_F0_Z` number: Mean fundamental frequency during /z/ phonation in Hz. Example: 195.8
  - `F0_STD_Z` number: Standard deviation of F0 during /z/ phonation in Hz. Example: 8.3
  - `F0_CV_Z` number: Coefficient of variation of F0 during /z/ in %. Example: 4.2
  - `RELIABILITY_SCORE` number: Composite reliability score (0-4). Example: 3.8
  - `PRESBYLARYNGIS_RISK` integer: Age flag (0/1), informational only: to our knowledge, no validated age-specific S/Z cut-off exists. Example: 0
  - `SZ_INTERPRETATION` string: Text label for the ratio; only the 1.4 cut-off has a published source (Eckel & Boone 1981). Example: "Normal S/Z ratio"
  - `CLINICAL_SIGNIFICANCE` string: Pathophysiology interpretation. Example: "No evidence of vocal fold mass lesions"
  - `RISK_LEVEL` string: Stratified risk assessment. Example: "Low"
  - `RELIABILITY` string: Test reliability classification. Example: "High reliability"
  - `AGE_ADJUSTMENT` string: Age-specific interpretation note. Example: "No age-related adjustments needed"
  - `GENDER` string: Gender classification. Example: "Female"
  - `PATIENT_AGE` integer: Patient age in years. Example: 35
  - `PATIENT_GENDER` string: Patient gender classification. Example: "Female"
  - `AGE_GROUP` string: Age-based clinical grouping. Example: "Young Adult"
  - `AGE_NOTE` string: Age-related clinical note. Example: "Age within normal vocal range"
  - `GENDER_NOTE` string: Gender-specific clinical note. Example: "Female-typical phonation patterns"
  - `EXPECTED_SZ_RANGE` string: Expected S/Z ratio range for demographics. Example: "0.85-1.15"
  - `PHONATION_QUALITY` string: Overall phonation quality assessment. Example: "Good phonatory control"

## 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)