`window` — discrete window functions

Purpose

Window functions taper the endpoints of each analysis frame so the FFT sees a periodic-looking signal rather than the abrupt discontinuities created by a rectangular slice. Tapering reduces spectral leakage at the cost of a small main-lobe widening, which is the standard trade-off used by every spectral analyzer in this package.

The module exposes three closed-form windows — Hann, Hamming, and Blackman — selectable by the window option of SpectrumAnalyzerOptions. Vectors are cached per (name, size) so the spectrum, spectrogram, and MFCC analyzers share a single allocation across every frame of the same shape.

Features

Hann, Hamming, Blackman generators producing Float32Array vectors.
Cached per (name, size) to avoid re-allocation on every frame.
applyWindow for in-place multiplication into a caller-provided buffer.
clearWindowCache for benchmarks measuring cold-start cost.

Usage: Basic

import {
  applyWindow,
  getWindow,
} from "@suaveplan/audio-analysis-spectrum/algorithms/window";

const w = getWindow("hann", 2048);
const frame = new Float32Array(2048);
const out = new Float32Array(2048);
applyWindow(frame, w, out);

Usage: Advanced

import {
  clearWindowCache,
  getWindow,
} from "@suaveplan/audio-analysis-spectrum/algorithms/window";

// Pre-warm the cache for the working set.
for (const name of ["hann", "hamming", "blackman"] as const) {
  for (const size of [1024, 2048, 4096]) getWindow(name, size);
}

// Later, before a benchmark, evict every vector.
clearWindowCache();

API Reference

getWindow(name, size): Float32Array — cached window vector.
applyWindow(frame, window, out): void — element-wise multiply.
clearWindowCache(): void — drop every cached vector.
WindowName = "hann" | "hamming" | "blackman".

Implementation Notes

Each closed form is the standard periodic definition with N - 1 in the denominator, so the endpoints of Hann and Blackman are exact zeros and the centre is exactly 1. Hamming uses the (0.54, 0.46) coefficients from Hamming's 1989 paper. The cache key is ${name}:${size}; since both inputs are tightly constrained by the analyzer layer the key set is small.

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window — discrete window functions