---
title: "Calculate jitter, shimmer, and recording quality metrics with clinical interpretation"
method: GET
path: "/api/jitter-shimmer"
tags: ["Advanced Voice Analysis"]
---

# Calculate jitter, shimmer, and recording quality metrics with clinical interpretation

`GET /api/jitter-shimmer`

## Request

- Base URL: `https://platform.vocametrix.com`
- URL: `https://platform.vocametrix.com/api/jitter-shimmer`
- Auth: API key in header `X-API-Key`

## Query parameters

- `svFileId` number, required

## Response `200`

Successful response

- object
  - `RECORDING_QUALITY` string: Quality assessment: "Good" (-25 to -10 dBFS), "Suboptimal" (-30 to -25 or -10 to -6 dBFS), "Poor" (<-30 or >-6 dBFS). Example: "Good"
  - `RECORDING_QUALITY_WARNING` string: Detailed warning message if quality is suboptimal or poor. Empty string if good. Example: "CAUTION: Recording level is low (<-25 dBFS). Consider re-recording with slightly higher volume for more reliable results."
  - `MEAN_INTENSITY_DBFS` number: Mean recording intensity in dBFS (decibels relative to full scale). Target range: -25 to -10 dBFS. Example: -18.3
  - `RMS_AMPLITUDE` number: Root-mean-square amplitude (0-1 scale). Used to calculate dBFS. Example: 0.122
  - `JITTER_LOCAL_PERCENT` number: Local jitter (period-to-period variation) in percent. Primary jitter measure. MDVP reference: 1.04% (not validated for Praat). Example: 0.85
  - `JITTER_PPQ5_PERCENT` number: 5-period perturbation quotient in percent. Smoothed jitter over 5 periods. Example: 0.78
  - `JITTER_RAP_PERCENT` number: Relative average perturbation in percent. Average over 3 consecutive periods. Example: 0.82
  - `JITTER_DDP_PERCENT` number: Difference of differences of periods in percent. Sensitive to small perturbations. Example: 1.23
  - `SHIMMER_LOCAL_PERCENT` number: Local shimmer (peak-to-peak amplitude variation) in percent. Primary shimmer measure. MDVP reference: 3.81% (not validated for Praat). Example: 2.45
  - `SHIMMER_LOCAL_DB` number: Local shimmer in decibels. Logarithmic amplitude perturbation. Example: 0.215
  - `SHIMMER_APQ3_PERCENT` number: 3-period amplitude perturbation quotient in percent. Short-term shimmer. Example: 2.31
  - `SHIMMER_APQ5_PERCENT` number: 5-period amplitude perturbation quotient in percent. Medium-term shimmer. Example: 2.38
  - `SHIMMER_APQ11_PERCENT` number: 11-period amplitude perturbation quotient in percent. Long-term shimmer trends. Example: 2.52
  - `SHIMMER_DDA_PERCENT` number: Difference of differences of amplitudes in percent. Sensitive to amplitude changes. Example: 3.47
  - `MEAN_F0` number: Mean fundamental frequency in Hz. Averaged across voiced segments. Example: 185.7
  - `F0_STD` number: Standard deviation of F0 in Hz. Pitch variability indicator. Example: 7.2
  - `F0_CV` number: Coefficient of variation of F0 in percent. (F0_STD / MEAN_F0) × 100. Pitch stability metric. Example: 3.88
  - `VOICELESS_PERCENT` number: Percentage of voiceless (unvoiced) frames. Indicates phonation breaks. Example: 5.2
  - `NUMBER_OF_PERIODS` number: Number of vocal fold vibration periods analyzed. Minimum 20 required, 100+ optimal. Example: 245
  - `INSUFFICIENT_PERIODS` integer: Flag indicating insufficient periods: 1 if <100 periods (reduced reliability), 0 if ≥100 periods. Example: 0
  - `JITTER_SEVERITY` string: Flag against the MDVP reference (not validated for Praat): "Normal" (≤1.04%) or "Elevated" (>1.04%). Example: "Normal"
  - `SHIMMER_SEVERITY` string: Flag against the MDVP reference (not validated for Praat): "Normal" (≤3.81%) or "Elevated" (>3.81%). Example: "Normal"
  - `JITTER_INTERPRETATION` string: Interpretation text for jitter results. Example: "At or below MDVP reference (1.04 %), not validated for Praat"
  - `SHIMMER_INTERPRETATION` string: Interpretation text for shimmer results. Example: "At or below MDVP reference (3.81 %), not validated for Praat"

## 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)