Time-compressed speech is a technique used, often in advertising, to make recorded speech contain more words in a given time, yet still be understandable.

History

Before electronic methods were developed, spokespeople who could talk extremely quickly and still be understood were widely used, especially for disclaimers.

Methods

• Removal of silences. There are normally silences between words and sentences, and even small silences within certain words. These can be reduced considerably and still leave an understandable result.

• Increasing speed. The speed can be increased on the entire audio track, but this has the undesirable effect of increasing the frequency, so the voice sounds high-pitched (like someone who has inhaled helium). This can be compensated for, however, by bringing the pitch back down to the proper frequency.

Advantages

The same number of words can be compressed into a smaller time, and thus reduce advertising costs, or more information can be included in a given radio or TV ad. Another advantage is that this method seems to make the ad louder (by increasing the average volume), and thus more likely to be noticed, without exceeding the maximum volume allowed by law.

Disadvantages

The effect of removing the silences and increasing the speed is to make it sound much more insistent, possibly to the point of unpleasantness.

Other uses

• Teaching and studying.

• Aids for users with visual impairments.

• Human-computer interfaces (such as voice-mail systems or lists of movies playing at a theatre)

Other terms

Unfortunately, there are a variety of confusing terms used for this and related technologies:

• Time-compressed/accelerated speech (often used in psychological literature)

• Compressed speech

• Time-scale modified speech (used in signal processing literature)

• time-scale modification (TSM)http://www.enounce.com/whatistsm.html

• Sped-up speech

• Rate-converted speech

• Time-altered speech

• Voice compression/speech compression/voice encoding/speech encoding
  Speech encoding
  Speech coding is the application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting...
  
  /audio compression (data) (these often refers to compression for transmission or storage, possibly to an unintelligible state, with decompression used during playback)

See also

• Some constructed language
  Constructed language
  A planned or constructed language—known colloquially as a conlang—is a language whose phonology, grammar, and/or vocabulary has been consciously devised by an individual or group, instead of having evolved naturally...
  
  s, such as Ithkuil
  Ithkuil
  Ithkuil is a constructed language marked by outstanding grammatical complexity, expressed with a rich phonemic inventory or through an original, graphically structured, system of writing....
  
   and Ceqli, are designed to be very concise.
• A proprietary implementation probably of the Synchronised OverLap Add method for speech compression that works on flash videos played in internet browsers. In this context the beta version is provided for free.