---
id: harmonics-to-noise-ratio
title: Harmonics-to-noise Ratio (HNR)
---

The harmonics-to-noise ratio (HNR), a common measurement of aspiration, quantifies the amount of additive noise in the voice signal.[^1]

[^1]: Ferrand, C. T. (2002). Harmonics-to-noise ratio: an index of vocal aging. Journal of voice, 16(4), 480-487.

## Raw Variables

| Variable      | Description |
| ----------- | ----------- |
| `aco_hnr`      | **Harmonics-to-noise ratio.** Frame-wise measurements of harmonics-to-noise ratio.    |

## Derived Variables

| Variable      | Description |
| ----------- | ----------- |
| `aco_hnr_mean`      | **Harmonics-to-noise ratio mean.** Mean of `aco_hnr` across the audio file.     |
| `aco_hnr_stdev`      | **Harmonics-to-noise ratio standard deviation.** Standard deviation of `aco_hnr` across the audio file.     |