DecibelMeter

Monitor dB Levels Using HTML5 Audio API

DecibelMeter allows you to monitor the noise level using your device's microphone(s) from within a web page or node-webkit application.

// connect to first audio input device found
new DecibelMeter.listenTo(0, (dB, percent, value) => console.log(dB))

Browser Support

I have tested this in Chrome and Firefox for Windows and Android. iOS support is not available yet.

Live Example

You can try the DecibelMeter now: DecibelMeter example

Installation

npm install --save decibel-meter

Usage Examples

Import DecibelMeter as ES6 module

import DecibelMeter from 'decibel-meter'

Or, using a script tag

<script src="decibel-meter.js"></script>

Create a decibel meter

const meter = new DecibelMeter('unique-id');

Get a list of audio sources on the device

// resolves with array of MediaDeviceInfo objects, filtered by type: audioinput
meter.sources.then(sources => console.log(sources))

Connect to an audio source

 
// first method
 
meter.sources.then(sources => {
    meter.connect(sources[0])
})
 
// second method
 
meter.connectTo('default') // find audioinput by deviceId, and connect if possible
meter.connectTo(0) // find the first audioinput, and connect if possible
 
// handling errors
 
meter.connectTo('not-real').catch(err => alert('Connection Error'))

Do something with the decibel data

const level = document.getElementById('db-level')
 
meter.on('sample', (dB, percent, value) => level.textContent = `${dB} dB`) // display current dB level

Start listening to audio source

meter.listen() // "sample" callback set above will now receive data

Stop listening to audio source

meter.stopListening()

Disconnect from the audio source entirely

meter.disconnect() // returns Promise

Connect to a source, add a 'sample' event listener, and start listening to the connected source, in one terse command

meter.listenTo(0, (dB, percent, value) => level.textContent = `${dB} dB`)

Multiple meters on one page

var meter1 = new DecibelMeter('meter-1')
var meter2 = new DecibelMeter('meter-2')
 
DecimelMeter.meters // all meters created on this page
 
meter1 === DecimelMeter.getMeterById('meter-1'); // true

Events

DecibelMeter has its own events dispatcher, and supports the following Events

• change
• connect
• disconnect
• sample

change - the meter's listening state has changed

meter.on('change', listening => {
    if (listening)
        level.classList.add('active')
    else
        level.classList.remove('active')
})

connect - the meter successfully connected to an audioinput

meter.on('connect', (source, previous) => {
    console.log(`
        Connected to ${source.label}
        Disconnected from ${previous.label}`
    )
})

disconnect - the meter was disconnected from a source

sample - the meter received decibel data from the source