Audio Processor

audio-processor.ts

import { FFT } from 'fft-js'; // This is a placeholder, ensure to use an appropriate FFT library
import * as fs from 'fs';
import { createReadStream, createWriteStream } from 'fs';
import { EventEmitter } from 'events';

const TwoPi = Math.PI * 2;
const FourPi = Math.PI * 4;
const FSam = 44100;
const nOLA = 2;
const nFFT = 2048;
const nFFT2 = nFFT / 2;
const nTap = nFFT2;
const nZero = nFFT2;
const nSam = nFFT - nZero;
const nShift = nSam / nOLA;

const Freq = [125, 187, 250, 375, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000, 12000, 16000];
const Smearing: number[] = [0.4, 0.5, 0.9, 1.2, 1.5, 1.8, 2.0, 2.3, 3.1, 3.9];

type RealArray = Float64Array;
interface Threshold { hearingLossDb: number[]; }

class AudioProcessor {
  private fft: FFT;
  private buffer: Int16Array;
  private windowFunction: RealArray;

  constructor() {
    this.fft = new FFT(nFFT);
    this.buffer = new Int16Array(nFFT);
    this.windowFunction = this.blackmanWindow();
  }

  private blackmanWindow(): RealArray {
    let window = new Float64Array(nFFT);
    for (let i = 0; i < nFFT; i++) {
      window[i] = 0.42 - 0.5 * Math.cos(TwoPi * i / nFFT) + 0.08 * Math.cos(FourPi * i / nFFT);
    }
    return window;
  }

  public lowPassTimeSeries(fc: number): RealArray {
    let fir = new Float64Array(nTap);
    let sum = 0;
    for (let i = 0; i < nTap; i++) {
      let x = fc * TwoPi * (i - nTap / 2);
      if (x === 0) {
        fir[i] = fc * TwoPi;
      } else {
        fir[i] = Math.sin(x) / x; // sinc(x)
      }
      fir[i] *= this.windowFunction[i];
      sum += fir[i];
    }
    for (let i = 0; i < nTap; i++) {
      fir[i] /= sum;
    }
    return fir;
  }

  public hearingLossFilter(yFir: RealArray, threshold: Threshold, ear: number): void {
    // Implement the filter logic based on hearing thresholds
  }

  public smearingFilter(wFft: RealArray, b: number): void {
    // Implement smearing filter logic
  }
}

// Usage of the class for audio processing
const audioProcessor = new AudioProcessor();