analyser-frequency-average/index.js

gets an average Hz between two frequency ranges

var frequencyToIndex = require('audio-frequency-to-index')

module.exports = analyserFrequencyAverage.bind(null, 255)
module.exports.floatData = analyserFrequencyAverage.bind(null, 1)

function analyserFrequencyAverage (div, analyser, frequencies, minHz, maxHz) {
  var sampleRate = analyser.context.sampleRate
  var binCount = analyser.frequencyBinCount
  var start = frequencyToIndex(minHz, sampleRate, binCount)
  var end = frequencyToIndex(maxHz, sampleRate, binCount)
  var count = end - start
  var sum = 0
  for (; start < end; start++) {
    sum += frequencies[start] / div
  }
  return count === 0 ? 0 : (sum / count)
}