SpeechRecognitionAlternative

The SpeechRecognitionAlternative interface of the Web Speech API represents a single word that has been recognised by the speech recognition service.

Properties

SpeechRecognitionAlternative.transcript Read only

Returns a string containing the transcript of the recognised word.

SpeechRecognitionAlternative.confidence Read only

Returns a numeric estimate of how confident the speech recognition system is that the recognition is correct.

Examples

This code is excerpted from our Speech color changer example.

recognition.onresult = function(event) {
  // The SpeechRecognitionEvent results property returns a SpeechRecognitionResultList object
  // The SpeechRecognitionResultList object contains SpeechRecognitionResult objects.
  // It has a getter so it can be accessed like an array
  // The first [0] returns the SpeechRecognitionResult at position 0.
  // Each SpeechRecognitionResult object contains SpeechRecognitionAlternative objects that contain individual results.
  // These also have getters so they can be accessed like arrays.
  // The second [0] returns the SpeechRecognitionAlternative at position 0.
  // We then return the transcript property of the SpeechRecognitionAlternative object
  var color = event.results[0][0].transcript;
  diagnostic.textContent = 'Result received: ' + color + '.';
  bg.style.backgroundColor = color;
}

Specifications

Specification	Status	Comment
Web Speech API The definition of 'SpeechRecognitionAlternative' in that specification.	Draft

Browser compatibility

• [1] Speech recognition interfaces are currently prefixed on Chrome, so you'll need to prefix interface names appropriately, e.g. webkitSpeechRecognition; You'll also need to serve your code through a web server for recognition to work.
• [2] Can be enabled via the media.webspeech.recognition.enable flag in about:config, although note that currently speech recognition won't work on Desktop Firefox — it will be properly exposed soon, once the required internal permissions are sorted out.

Firefox OS permissions

To use speech recognition in an app, you need to specify the following permissions in your manifest:

"permissions": {
  "audio-capture" : {
    "description" : "Audio capture"
  },
  "speech-recognition" : {
    "description" : "Speech recognition"
  }
}

You also need a privileged app, so you need to include this as well:

  "type": "privileged"

See also

• Web Speech API