---
title: "Calculate formant-corrected H1*-H2* voice source measure"
method: GET
path: "/api/calculate-h1-h2"
tags: ["Advanced Voice Analysis"]
---

# Calculate formant-corrected H1\*-H2\* voice source measure

`GET /api/calculate-h1-h2`

## Request

- Base URL: `https://platform.vocametrix.com`
- URL: `https://platform.vocametrix.com/api/calculate-h1-h2`
- Auth: API key in header `X-API-Key`

## Query parameters

- `svFileId` string, required
- `gender` string, required

## Response `200`

Successful response

- object
  - `H1_H2` number: Raw (uncorrected) H1-H2 in dB. Amplitude difference between first and second harmonics without formant correction. Use for comparison with corrected value. Example: 5.88
  - `H1_H2_CORRECTED` number: Formant-corrected H1*-H2* in dB. Primary measure accounting for vocal tract resonance effects using Iseli & Alwan (2004) algorithm. Higher values may indicate breathier voice quality. Example: 10.93
  - `MEAN_F0` number: Mean fundamental frequency in Hz. Averaged across all valid frames in the stable vowel portion. Example: 134.76
  - `F1_MEAN` number: Mean first formant frequency in Hz. Extracted using Praat Burg algorithm. Vowel height correlate. Example: 473.00
  - `F2_MEAN` number: Mean second formant frequency in Hz. Extracted using Praat Burg algorithm. Vowel frontness/backness correlate. Example: 1183.97
  - `B1_MEAN` number: Estimated first formant bandwidth in Hz. Calculated with the Hawks & Miller (1995) bandwidth: 5th-order polynomial in the formant frequency (separate coefficients below and above 500 Hz), scaled by S = 1 + 0.25 × (F0 − 132) / 88; coefficients as in VoiceSauce. Used for formant correction. Example: 36.95
  - `B2_MEAN` number: Estimated second formant bandwidth in Hz. Calculated with the Hawks & Miller (1995) bandwidth: 5th-order polynomial in the formant frequency (separate coefficients below and above 500 Hz), scaled by S = 1 + 0.25 × (F0 − 132) / 88; coefficients as in VoiceSauce. Used for formant correction. Example: 43.28
  - `FRAMES_ANALYZED` number: Number of valid frames analyzed. Frame shift = 1ms, window = 3 pitch periods. Higher counts indicate longer recordings or more stable voicing. Example: 2977
  - `GENDER` string: Gender classification used for formant analysis. Determines formant ceiling frequency. Example: "Male" or "Female (F0-based)"

## 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)