Building a Kotlin Voice Assistant

A voice assistant is a software application that can understand and respond to voice commands. In this guide, we'll explore how to build a Kotlin voice assistant using speech recognition and natural language processing libraries.

Setting Up Your Environment

Before you start, make sure you have the following tools and libraries installed:

  • Kotlin
  • An integrated development environment (IDE) like IntelliJ IDEA
  • Speech recognition library for Kotlin (e.g., CMU Sphinx or Google Cloud Speech-to-Text)
  • Natural language processing library for Kotlin (e.g., OpenNLP or Stanford NLP)
  • Text-to-speech library for Kotlin (e.g., Google Text-to-Speech or FreeTTS)

Step 1: Set Up Speech Recognition

Integrate a speech recognition library into your Kotlin project. Configure it to capture and transcribe voice commands. Here's a basic example using CMU Sphinx:

import edu.cmu.sphinx.api.Configuration
import edu.cmu.sphinx.api.StreamSpeechRecognizer
fun main() {
val configuration = Configuration()
configuration.acousticModelPath = "resource:/edu/cmu/sphinx/models/en-us/en-us"
configuration.dictionaryPath = "resource:/edu/cmu/sphinx/models/en-us/cmudict-en-us.dict"
configuration.languageModelPath = "resource:/edu/cmu/sphinx/models/en-us/en-us.lm.bin"
val recognizer = StreamSpeechRecognizer(configuration)
// Initialize and capture audio input for speech recognition
val result = recognizer.getResult()
val recognizedText = result.hypothesis()
println("You said: $recognizedText")

Step 2: Implement Natural Language Processing

Use a natural language processing library to understand the meaning of recognized text. Extract user intent and information. Here's a basic example using OpenNLP:

fun main() {
val modelIn = javaClass.getResourceAsStream("/en-parser-chunking.bin")
val model = ParserModel(modelIn)
val parser: Parser = ParserFactory.create(model)
val inputText = "What's the weather like today?"
val parse = parser.parse(inputText) // Extract intent and entities from the parsed tree
println("User intent: CheckWeather, Location: CurrentLocation")

Step 3: Implement Text-to-Speech

Add a text-to-speech library to your Kotlin project. Use it to generate voice responses. Here's a basic example using Google Text-to-Speech:

fun main() {
val textToSpeechClient = TextToSpeechClient.create()
val input = SynthesisInput.newBuilder().setText("The weather today is sunny.")
val voice = VoiceSelectionParams.newBuilder().setLanguageCode("en-US")
val audioConfig = AudioConfig.newBuilder().setAudioEncoding(AudioEncoding.LINEAR16)
val response = textToSpeechClient.synthesizeSpeech(input, voice, audioConfig) // Play the generated audio response

Step 4: Create Voice Assistant Logic

Combine the components to create the logic for your voice assistant. Recognize voice commands, process them using natural language processing, and generate voice responses.

Step 5: Test and Refine

Test your voice assistant with various voice commands. Refine its responses and logic to improve user experience and accuracy.


Building a Kotlin voice assistant involves combining speech recognition, natural language processing, and text-to-speech components. This guide provides a basic introduction to creating a voice assistant in Kotlin. Depending on your project's complexity, you may need to explore advanced speech recognition and NLP techniques to enhance your voice assistant's capabilities.

Happy building your Kotlin voice assistant!