goertzel

> Implements the Goertzel
algorithm for efficient
frequency detection.

example

``js
var goertzel = require('goertzel')

var opts = {
// 1 kHz
targetFrequency: 1000,
// samples per second
sampleRate: 10000,
// samples per frame
samplesPerFrame: 100
}

var detect = goertzel(opts)

// generate sine wave at some Hz and time (ms)
function sin (hz, t) {
return Math.sin(Math.PI 2 t * hz)
}

// sine at 1 kHz for 100 samples
var data = []
for (var i = 0; i < opts.samplesPerFrame; i++) {
var v = sin(opts.targetFrequency, i / opts.sampleRate)
data.push(v)
}

console.log(detect(data))
`

`
true
`

methods

var detect = goertzel(opts={})

Returns a function set to detect a single frequency.

opts is mandatory, and has some required and optional parameters:

- opts.targetFrequency (required) - the frequency, in Hertz, to detect the
presence of
- opts.sampleRate (required) - how many samples are taken per second. For best
results, this should be at least twice the Nyquist
frequency. 2.5x works well.
- opts.samplesPerFrame (required) - how many samples will be included in each
frame to be tested.
- opts.threshold (optional) - The Goertzel algorithm returns a relative
magnitude of how well the samples match the targetFrequency. Set this to
control the threshold. In general, the default value can be used safely.

detect(data)

Returns a boolean: true if the targetFrequency is present in the samples,
and false otherwise.

data is expected to be compatible with a Float32Array.

install

With npm installed, run

`
$ npm install goertzel
``

license

MIT