AI-driven Speech Synthesis

Have you ever wondered how the voices from automated responders, smart speakers, and navigation systems are created?

AI now possesses the capability to mimic human voices. It can generate not only simple mechanical sounds but also replicate emotions, intonations, and even imitate specific people's voices.

Speech Synthesis is the technology that enables computers to generate speech by mimicking human voices.

AI learns from large volumes of voice data by analyzing sound and sentence patterns, applying them to produce new speech.

Speech synthesis technology typically converts input text into human-like speech, known as Text-to-Speech (TTS).

In this lesson, we will explore the concept of speech synthesis and the technical processes AI uses to create speech.

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Computers cannot directly interpret written text. The process begins with a text preprocessing stage that breaks sentences into smaller, analyzable units.

Tokens are the smaller units obtained by breaking down a sentence.

For example, when tokenizing "Hello, how are you?", it can be split into ["Hello", ",", "how", "are", "you", "?"].

The characters are converted into phonemes, which are units that can be pronounced. Common systems for this include ARPAbet or the International Phonetic Alphabet (IPA).

For instance, "Hello" is converted to HH AH0 L OW1 in the ARPAbet format that machines easily understand.

It involves analyzing which parts of a sentence should be emphasized or the flow of the sentence.

"I am going to school." has a declarative intonation, whereas "Am I going to school?" has an interrogative intonation.

AI learns these differences in intonation to generate speech that matches the tone of the sentence.

The initial audio data generated by AI is not immediately audible as natural speech. A Vocoder is used to convert this data into realistic, human-like voice output.

It generates speech by modeling the frequency and amplitude characteristics of human vocal signals.

Recently, deep learning-based vocoders like WaveNet and HiFi-GAN have become widely used, creating voices so natural that they're nearly indistinguishable from human speech.

AI-based speech synthesis continues to evolve, enabling increasingly natural pronunciation and expressive intonation.

In the next lesson, we will recap what we've learned and reinforce key concepts through a quiz.