Technology: Talking advertisement argues advantages of new speech synthesis

日期:2019-02-28 10:08:12 作者:荆潺 阅读:

By BARRY FOX READERS of a recent edition of Business Week have been hearing the world’s first talking advertisement, promoting Texas Instruments’ developments in speech synthesis technology. As the pages of the magazine open, a small pressure-sensitive switch closes to connect three button cell batteries to a voice synthesis circuit, an amplifier and a piezoelectric loudspeaker 2.5 centimetres in diameter. After a short interval, a metallic male voice speaks 42 words of advertising puff in 15 seconds. The new system is a cheap version of speech-synthesis circuitry that was developed 10 years ago for educational toys. The system relies on a technique called linear predictive coding. It is impractical to reproduce speech from microchip circuits by the conventional solid-state recording technique of converting live analogue speech into digital code, storing the code in a computer memory and then converting it back into analogue form for replay. Too much expensive memory is needed to store even a short sentence. Linear predictive coding works differently. A sound synthesis circuit generates raw noise signals, which are then fed to a filter which alters the character of the noise to mimic human speech or animal noises. The effect is as if hiss noises were fed through a hi-fi system and the volume and tone controls juggled. The filter in the synthesis circuit is controlled by a string of digital code instructions stored in a solid-state memory, and released at the pace of speech. Because the stored instructions need only control changes in the filter setting, a small amount of code can produce a large number of vowels and consonants. This reduces the memory capacity needed to store useful quantities of sound, which in turn reduces the cost. It says that a complete talking advertisement, as incorporated in Business Week, including memory store, synthesis circuit, batteries, loudspeaker and switch can be produced for as little as $4. The magazine advertisement, like TI’s talking toys, sounds more like a lisping Dalek than a human being. But the words are clearly intelligible and instantly recognisable as male rather than female. TI’s advert will surely irritate readers of the magazine, much like musical Christmas cards. There is also a more serious problem for the security services. The talking advertisement, which looks and feels like a thick credit card, may prove hard to distinguish from a terrorist’s letter bomb. By the same token,