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How is coherence measured in HeartMath devices?

Coherence Scoring System

Introduction

Coherence measurement is a core feature of HeartMath technologies, focused on tracking heart rhythm patterns using specialized pulse sensors. Understanding how coherence is determined and displayed can help users optimize their stress management and heart-brain synchronization practices.

How the Pulse Sensor Works

  • The HeartMath pulse sensor uses infrared (IR) light emitted into the earlobe.

  • An IR sensor on the opposite side of the earlobe detects the transmitted light.

  • Blood density in the earlobe fluctuates with each heartbeat, modulating the amount of IR light that passes through.

  • These modulations in IR light intensity are converted into electrical signals that represent the pulse wave.

Pulse Signal Processing

  • The time between pulse signals (inter-beat intervals, IBI) is calculated and displayed as a Heart Rate Variability (HRV) strip chart.

  • Continuous streams of IBI data are used for further analysis to determine coherence scores.

Calculating Coherence

  • Coherence is measured by analyzing the most recent 64 seconds of IBI data.

  • A power spectrum is calculated from the IBI signal.

  • High coherence: Most of the power is concentrated in or around a single peak in the coherence frequency range, indicating a regular, sine-wave-like heart rhythm.

  • Low coherence: Power is spread across multiple peaks; the rhythm is less regular.

Scoring and Display

  • Coherence level is recalculated every 5 seconds by comparing the power in the main coherence peak to the remaining spectrum.

  • The coherence score is generated using a logarithmic transformation of this ratio.

  • These scores drive various software displays that help users visualize and track their coherence levels in real time.

Summary

The HeartMath coherence score provides an objective and visual indicator of heart rhythm regularity, supporting self-regulation and stress management practices. Understanding sensor operation and coherence calculations enables more effective use of HeartMath tools for personal well-being and scientific study.