Speech and Language AI
Speech AI converts audio to text (speech recognition) and text to audio (text-to-speech). Combined with NLP, these technologies power voice assistants and accessibility tools.
10 min•By Priygop Team•Updated 2026
Speech Recognition (STT)
Speech recognition converts audio waves into text.
The process:
1. Audio is recorded as a waveform (sequence of numbers representing sound pressure over time)
2. The audio is split into short segments (typically 25ms each)
3. Each segment is converted into a spectrogram (a visual representation of frequency over time)
4. A deep learning model (often a Transformer) reads the spectrogram and predicts the spoken words
Applications: dictation, voice search, meeting transcription, accessibility for people who cannot type.
Diagram
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Deep Learning ⊂ Machine Learning ⊂ Artificial Intelligence
Text-to-Speech (TTS)
- Text-to-speech converts written text into natural-sounding audio
- Modern TTS models (like those from ElevenLabs, OpenAI, and Google) produce nearly human-quality speech
- TTS is used in screen readers, navigation apps, audiobook generation, and voice assistants
- Voice cloning TTS can reproduce a specific person's voice style from a few minutes of audio samples
- This raises ethical concerns about deepfakes and consent, which we will discuss in Module 12
Voice Assistant Pipeline
Voice Assistant Pipeline
# The complete voice assistant pipeline
def voice_assistant_pipeline(audio_input):
"""
Illustrates the steps in a voice assistant response.
In real systems, each step uses a specialized model.
"""
print("Voice Assistant Pipeline:")
print()
# Step 1: Speech to Text
# Real: Whisper or similar ASR model processes audio waveform
transcribed_text = "What is the weather like today in London?"
print(f"Step 1 - Speech Recognition:")
print(f" Audio -> '{transcribed_text}'")
print()
# Step 2: Intent Understanding (NLP)
# Real: NLP classifier identifies intent and entities
intent = "weather_query"
entities = {"location": "London", "time": "today"}
print(f"Step 2 - Intent and Entity Extraction:")
print(f" Intent: {intent}")
print(f" Entities: {entities}")
print()
# Step 3: Action / API Call
# Real: query a weather API
weather_data = {"temp": "15C", "condition": "partly cloudy", "rain": "20%"}
print(f"Step 3 - Action (Weather API call):")
print(f" Result: {weather_data}")
print()
# Step 4: Response Generation (NLP)
response = f"Today in London it is {weather_data['temp']} and {weather_data['condition']}, with a {weather_data['rain']} chance of rain."
print(f"Step 4 - Response Generation:")
print(f" '{response}'")
print()
# Step 5: Text to Speech
print(f"Step 5 - Text-to-Speech:")
print(f" Text -> [Audio waveform spoken aloud to user]")
print()
return response
# Run the pipeline
result = voice_assistant_pipeline("audio_waveform_data")
print(f"Final spoken response: '{result}'" )Key Takeaways
- Speech AI converts audio to text (speech recognition) and text to audio (text-to-speech).
- Text-to-speech converts written text into natural-sounding audio
- Modern TTS models (like those from ElevenLabs, OpenAI, and Google) produce nearly human-quality speech
- TTS is used in screen readers, navigation apps, audiobook generation, and voice assistants