FrequencyData

Info

FrequencyData contains the frequency analysis results from the current audio frame. It includes a downsampled spectrum array, the dominant frequency, and a list of the strongest frequency peaks. This is one of three analysis dimensions returned by AudioAnalysisResult.

Properties

Property	Type	Description
spectrum	number[]	Frequency spectrum amplitude array, downsampled to 512 bins. Each element represents the amplitude at a frequency band.
dominantHz	number	The frequency with the highest amplitude in the current frame, in Hertz (Hz).
topFrequencies	FrequencyPeak[]	Array of the strongest frequency peaks, sorted by magnitude in descending order.

Note

The spectrum array has a fixed length of 512 elements. Each bin covers a frequency range determined by the sample rate and FFT window size of the native analyzer. The first bin corresponds to the lowest frequency and the last bin to the highest.

Usage

FrequencyData is accessed via result.frequency on an AudioAnalysisResult object. Use it for:

• Rendering frequency bar charts or spectrograms
• Identifying the dominant tone or instrument
• Detecting bass drops, vocal presence, or specific frequency patterns

Tips

For most visualization use cases, topFrequencies is more efficient than iterating the full spectrum array. It contains only the most significant peaks and is already sorted by magnitude.

Example

TypeScript

import { getResult, FrequencyData } from '@eisland/windows-volume-analyzer';

const result = getResult();
const freq: FrequencyData = result.frequency;

// Display the dominant frequency
console.log(`Dominant: ${freq.dominantHz.toFixed(1)} Hz`);

// Render a simple bar chart from the spectrum (first 32 bins)
const bars = freq.spectrum.slice(0, 32).map((v) => '█'.repeat(Math.round(v * 20)));
console.log(bars.join(''));

// Show top 3 peaks
for (const peak of freq.topFrequencies.slice(0, 3)) {
  console.log(`Peak: ${peak.hz.toFixed(1)} Hz (mag: ${peak.magnitude.toFixed(3)})`);
}

JavaScript

const { getResult } = require('@eisland/windows-volume-analyzer');

const result = getResult();
const freq = result.frequency;

// Display the dominant frequency
console.log(`Dominant: ${freq.dominantHz.toFixed(1)} Hz`);

// Render a simple bar chart from the spectrum (first 32 bins)
const bars = freq.spectrum.slice(0, 32).map((v) => '█'.repeat(Math.round(v * 20)));
console.log(bars.join(''));

// Show top 3 peaks
for (const peak of freq.topFrequencies.slice(0, 3)) {
  console.log(`Peak: ${peak.hz.toFixed(1)} Hz (mag: ${peak.magnitude.toFixed(3)})`);
}

Notes

Note

When no audio is playing, spectrum will be an empty array, dominantHz will be 0, and topFrequencies will be empty. Always check for empty data before processing.

Tips

If you only need the dominant frequency for simple visualizations (e.g. a single color that shifts with pitch), use dominantHz directly instead of processing the full spectrum array.

Important

The spectrum values are normalized amplitudes, not decibels. They are suitable for relative comparison within a frame but should not be treated as absolute measurements across frames.

Danger Avoidance

Caution

Do not assume spectrum always has 512 elements. While the analyzer targets 512 bins, the array may be empty when no audio is captured. Always check spectrum.length before indexing.