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https://github.com/hackergrrl/goertzel
:microphone: Fast frequency detection using the Goertzel algorithm.
https://github.com/hackergrrl/goertzel
Last synced: 1 day ago
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:microphone: Fast frequency detection using the Goertzel algorithm.
- Host: GitHub
- URL: https://github.com/hackergrrl/goertzel
- Owner: hackergrrl
- License: mit
- Created: 2016-01-29T18:54:04.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2016-06-10T17:07:52.000Z (over 8 years ago)
- Last Synced: 2024-09-23T22:32:44.370Z (10 days ago)
- Language: JavaScript
- Homepage:
- Size: 11.7 KB
- Stars: 10
- Watchers: 4
- Forks: 5
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
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README
# goertzel
> Fast frequency detection using the Goertzel algorithm
## Background
The [Goertzel algorithm](https://en.wikipedia.org/wiki/Goertzel_algorithm) is a
fast alternative to the [Fast Fourier Transform]() that is optimized for
detecting the presence of a single frequency in a buffer of signal samples
(radio waves, sound, light).
## Usage
Let's detect a sine wave with a frequency of 2 kHz:
```js
var goertzel = require('goertzel')
var detect = goertzel({
targetFrequency: 2000, // 2 kHz
sampleRate: 10000, // 1000 samples per second
samplesPerFrame: 100 // 100 samples per buffer
})
// Generates a sine wave at some Hz and time (ms)
function sin (hz, t) {
return Math.sin(Math.PI * 2 * t * hz)
}
// Populate a buffer with a sine wave at 2 kHz for 100 samples
var sin2 = []
for (var i = 0; i < 100; i++) {
var v = sin(2, i / 100)
sin2.push(v)
}
// Populate a buffer with a sine wave at 19 kHz for 100 samples
var sin19 = []
for (var i = 0; i < 100; i++) {
var v = sin(19, i / 100)
sin19.push(v)
}
console.log(detect(sin19))
console.log(detect(sin2))
```
This will output
```
false
true
```
## API
```js
var goertzel = require('goertzel')
```
### 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.
- `opts.sampleRate` (required) - how many samples are taken per second. For best
results, this should be at least twice the [Nyquist
frequency](https://en.wikipedia.org/wiki/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)
Given a buffer of floating point audio samples (-1..1), returns a `boolean`:
`true` if the `targetFrequency` is present in the samples, and `false`
otherwise.
## Install
With [npm](https://npmjs.org/) installed, run
```
$ npm install goertzel
```
## Acknowledgments
An understanding of the algorithm was gleaned from
https://en.wikipedia.org/wiki/Goertzel_algorithm and
http://www.embedded.com/design/configurable-systems/4024443/The-Goertzel-Algorithm.
## Works Great With
- [noffle/mic-stream](https://github.com/noffle/mic-stream)
## License
MIT