What is text to speech
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19 January 2010
A common question that comes up when people are shopping for GPS devices is “What is text-to-speech?”. The follow-up to that question then becomes “Do you think text-to-speech is a necessary feature?”. The answer will likely depend on the types of areas you drive in as well as your driving habits and your familiarity with the area. But let’s get back to the original question. Tone Prompts Tone prompts are commonly found on handheld GPS devices designed for outdoor use. These devices do not have auto navigation as their primary function, and thus they often lack many of the advanced features of true auto GPS navigations systems. Tone prompts are a set of tones that the device sounds out as you need to make turns at intersections. For example a device might give one tone just before you need to turn left, beep twice just before you need to turn right, and make one long beep just at the turn. This isn’t an ideal situation if you are using that device frequently for auto navigation. Voice Prompts Voice prompts are the most common form of cues on auto GPS devices. A voice prompt will typically give information such as the distance you need to cover and the direction you need to go in. For example a voice prompt might say “In 500 feet, turn right” and then at the turn say “Turn right”. Since there are not a lot of unique phrases that are spoken, these voice prompts are recorded ahead of time and are not customizable. When the time comes to give a direction, the device simply plays the pre-recorded audio. Text-to-speech Text-to-speech takes voice prompts to the next level. Instead of saying something generic like “In 500 feet, turn right” it can be more specific and will say “In 500 feet, turn right on High Street”. In this case, since there are thousands of street names, it can’t possibly store all of the combinations of directions within the device. Therefore the device is programmed to provide “speech synthesis” and the internal computer looks at the text (words, street names) that needs to be said and figures out how to pronounce those names. As a result, you will sometimes find that the way the device pronounces a street name isn’t exactly how you would pronounce it. Likewise, the sound quality of the voice sometimes isn’t quite as good as those without text-to-speech since the speech needs to be generated in real-time and there is no option for pre-recording. Want to hear a sample of the sound? The audio file below is a sample of text-to-speech from the TomTom 910. Is text-to-speech for me? That depends. In many driving environments, having the device say “turn left in 1,000 feet” followed by “turn left” just before the intersection is enough of a cue. If there is any confusion about exactly which street to turn on you could take a quick glance over at the display, or ask a passenger to look at the display and give you assistance. For many people, text to speech isn’t necessary. However if you live in an area where there are lots of streets close together, intersections where more than two streets converge, or don’t normally have someone else in the car to help look at the display, text-to-speech can be a nice option to have. One other word of caution. A street can often be known by more than one name. Numbered roads often have a “local” name they also go by. And sometimes roads can have more than one common name. Thus even with text-to-speech your GPS might say “turn right on US route 1″ while the street sign says “High Street”…. And both can be correct. The GPS will typically just pick one name to use. This might still require you to view the map display and use the distance cues provided. Another instance where Text to Speech can be less than helpful is in cases where you can’t find a street sign, the sign is missing, or when it is dark out. If the GPS says “turn right in 500 feet” then you will know it is the street about 500 feet in front of you. However if the GPS says “turn right on Elm Street” and you can’t find the street signs– that instruction won’t be as useful as one that tells you the distance. However in some cases text to speech voices will speak both the distance and the street name which should eliminate ambiguity. Text-to-speech typically ads a small amount to the price of the GPS over devices with simple verbal cues, however in some situations it can be well worth the extra cost.
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