freqr

Compute the frequency response of a digital filter.

Installation

npm install freqr

Quick Example

const freqr = require("freqr");

// type: "lowpass", freq: 2400hz, Q: 8
const b = [ 0.027136,  0.054272, 0.027136 ];
const a = [ 1.000000, -1.766316, 0.874860 ];

for (let f = 0; f < 0.2; f += 0.0025) {
  const res = freqr(b, a, f);

  console.log(res);
}

API

• freqr(b, a, f)
  • b: number[] - coefficients of feedforward
  • a: number[] - coefficients of feedback
  • f: number - normalized frequency [0..1]
    • f = frequency / sampleRate
  • returns
    • mag: number
    • phase: number
    • db: number
      • db = 20 * Math.log(mag) / Math.LN10

License

MIT