||This article possibly contains original research. (August 2008)|
Time-compressed speech is a technique used, often in television and radio advertising, to make recorded speech contain more words in a given time, yet still be understandable. The process is commonly used for "small print" caveats at the end of commercials. Before electronic methods were developed, spokespeople who could talk extremely quickly and still be understood were widely used, especially for disclaimers.
Speech can be compressed by removing silence or increasing its speed. There are normally silences between words and sentences, and even small silences within certain words, both of which can be reduced considerably and still leave an understandable result. The speed of a recording can be increased on the entire audio track, but this has the undesirable effect of increasing the frequency, making voices sound high-pitched. This can be compensated for, however, by bringing the pitch back down to the proper frequency.
The advantage of time-compressed speech is that the same number of words can be compressed into a smaller time, reducing advertising costs, or allowing more information to be included in a given radio or TV advertisement. Another advantage is that this method seems to make the ad louder by increasing its average volume, and thus more likely to be noticed, without exceeding the maximum volume allowed by law. Removing the silences and increasing the speed can make a piece of speech sound more insistent, possibly to the point of unpleasantness.
The process can also be used for teaching and studying, aiding users with visual impairments or optimising human-computer interfaces (such as voice-mail systems or lists of movies playing at a theatre).