Texas Instruments LPC Speech Chips

TI SpeakSpell no shadow

Texas Instruments LPC Speech Chips are a series of integrated circuits developed by Texas Instruments (TI) that are designed for speech synthesis and speech processing. These chips utilize Linear Predictive Coding (LPC), a method for compressing audio data, especially speech. LPC is a technique that models the human vocal tract as a series of digital filter coefficients, making it possible to reproduce speech with relatively low bit rates. The Texas Instruments LPC Speech Chips were groundbreaking in the 1970s and 1980s, finding applications in various consumer products, including toys, educational devices, and video games.

History

The development of the LPC Speech Chips by Texas Instruments began in the early 1970s, with the aim of creating cost-effective solutions for incorporating speech into electronic devices. The first commercially successful product to use these chips was the Speak & Spell, launched in 1978. This educational toy was revolutionary, as it was one of the first consumer products to feature a human-like voice. Following the success of the Speak & Spell, TI expanded the use of its speech synthesis technology into other products, including the Speak & Read, Speak & Math, and various speaking calculators.

Technology

The core technology behind the LPC Speech Chips involves Linear Predictive Coding, where the speech signal is approximated using a linear sum of past samples. The chips contain a small microprocessor that executes algorithms to synthesize speech from stored data. This data represents the LPC coefficients, pitch, and timing information necessary to reconstruct the speech signal. The chips are capable of generating speech by calculating the LPC coefficients in real-time or by retrieving pre-calculated coefficients from an external memory.

Models

Several models of the LPC Speech Chips were developed, each with improvements in memory, sound quality, and capabilities. Some of the notable models include:

- **TMS5100**: The first LPC speech synthesis chip, introduced in the late 1970s. It was used in the original Speak & Spell. - **TMS5200**: An improved version with better sound quality and more memory, used in later versions of Speak & Spell and other toys. - **TMS5220**: Known for its use in arcade games and home computers, offering further improvements in speech quality.

Applications

The LPC Speech Chips found their way into a wide range of applications beyond educational toys. They were used in:

- **Video Games**: Some arcade games and home video game consoles used LPC chips for speech synthesis to enhance gameplay with voice commands or feedback. - **Telecommunications**: Early voice response systems and voicemail systems utilized LPC technology for storing and compressing speech. - **Automotive**: Some car navigation and alert systems used speech chips for verbal instructions and warnings.

Legacy

The Texas Instruments LPC Speech Chips played a significant role in the history of electronic speech synthesis. They demonstrated the potential of digital speech processing in consumer products, paving the way for the development of more advanced speech synthesis and recognition technologies. Today, while more sophisticated algorithms and powerful processors have surpassed the capabilities of these early chips, the pioneering work of Texas Instruments in the field of speech synthesis remains a critical milestone in the evolution of digital speech technology.