Text to Speech Basics: What is TTS and Who Uses It? (2023)

The Internet of Speech is here, transforming the way we interact with our devices.

Siri tells you your next move in an unfamiliar city. The Google Assistant searches the web for instructions on how to grill salmon and reads them to you as you work. The voice robot at the other end of the customer service line delivers results without waiting or menus at the push of a button. Call it the Conversational Computing Era andThe end of these computer conversations is achieved through a digital technology called Text-to-Speech, or TTS for short.

But TTS isn't just for fancy new voice computing applications. It has been used as an accessibility tool for years; as educational technology (edtech); and as an audio alternative to reading. 2021 almost oneAdult dormitory in USAListening to audiobooks and TTS may have helped make these experiences possible. All of these examples just scratch the surface of what TTS can do.

In this article, we describe the standard meaning of text-to-speech and list some of the demographics that benefit from TTS. Below, we'll take a look at some of the ways organizations can use voice technology to achieve mission-critical goals. Finally, we will show you the history of this constantly evolving field. Here's your definitive introduction to TTS technology, starting with a basic question:

What is TTS? In other words, what does TTS stand for?

Curious to know what today's leading TTS actually sounds like?Discover ReadSpeaker's TTS voices, complete with audio samples.

Text to Speech: meaning and science behind the term

Text-to-speech technology is software that takes text as input and produces audible speech as output. In other words, it goes from text to speech, making TTS one of the best-equipped technologies of the digital revolution. A TTS system includes software that predicts the best possible pronunciation of a given text. It also contains the program that generates speech sound waves; this is called avoice changer

Text-to-speech is a multidisciplinary field that requires in-depth knowledge of a variety of sciences. If you want to build a TTS system from scratch, you need to study the following topics:

1. Linguistics, the scientific study of language.In order to synthesize coherent speech, TTS systems need a way to recognize how a human speaker pronounces written speech. This requires knowledge of linguistics down to the level of the phoneme, the sound units that together make up language, like the /c/ sound in cat. In order to achieve a truly realistic TTS, the system must also predict correct prosody, which includes speech elements beyond the phoneme, such as accents, pauses, and intonation.
2. Audio signal processing, creation and editing of digital sound representations.Audio (speech) signals are electronic representations of sound waves. The speech signal is represented digitally as a sequence of numbers. In the context of TTS, linguists use different feature representations that describe discrete aspects of the speech signal, making it possible to train AI models to generate new speech.
3. Artificial intelligence, specifically deep learning, a type of machine learning that uses a computing architecture called a deep neural network (DNN).A neural network is a computational model inspired by the human brain. It consists of complex networks of processors, each of which performs a processing task before sending its output to another processor. A trained DNN will learn the best processing route to get accurate results. This model offers a lot of computational power, making it ideal for handling the large number of variables required for high-quality speech synthesis.

ReadSpeaker's linguists conduct research and practice in all of these areas and continuously develop TTS technology. These researchers create lifelike TTS voices for brands and developers that enable businesses to differentiate themselves in the web of speech, whether on a smartphone, through smart speakers, or in a speech-enabled mobile app. In fact, TTS voices are emerging on an ever-widening range of devices and for an ever-increasing number of applications (and users).

Who Uses TTS?

People with visual and reading disabilities were the first to embrace the TTS. It makes sense: TTS makes the internet experience easier for 1 in 5 people with dyslexia. It also helps readers with low literacy skills and people with learning disabilities by taking the stress out of reading and presenting information in an optimal format. We are moving towards a more accessible Internet of the future and TTS is an integral part of that movement.

Many forward-thinking publishers and content owners are already offering TTS solutions to make the web a place for everyone. Businesses and buildings are required to provide access for wheelchair users and people with reduced mobility. Shouldn't the Internet be accessible to everyone? However, as technology advances, the uses and users of TTS also evolve. You may not need TTS, but you certainly will. Text-to-speech can make life easier and more efficient, no matter how you define it.

These are just some of the demographics already benefiting from TTS technology:

1. Students

current studiessuggest that students benefit more from combined presentations. Some students retain more information presented in audio and visual formats, also known asBimodal Learning.A popular educational structure calledUniversal Design for Learning (UDL)recommends dual modal learning to help all students succeed. Teachers at all grade levels promoting UDL use a combination of auditory, visual and kinesthetic techniques with the help of technology and adaptive lesson plans.

Even if you identify as a kinesthetic or visual learner, science says adding an auditory method can help you retain information. And at least TTS makes checking a lot more manageable.

2. Reader on the go

If you want to catch up on what's new, podcasts and audiobooks will only get you so far. So if a detailed profile inthe New Yorkeror a long articleThe guardwant to read, TTS can recite it for you. So you can drive, exercise or clean at the same time. Or maybe you prefer listening to reading. In accordance withthe best experts in technology,Online content will soon be automatically converted to audio so more people can enjoy content on the go.

3. Multitasking

The shortcuts TTS can provide are endless, from reading recipes while cooking to dictating instruction manuals while assembling furniture. The only limit to how much this can help is your own imagination.

4. Mature readers

Older adults understandably want to avoid straining their eyes to read small text on a smartphone. Text-to-speech can alleviate this problem by making online content easy to consume, regardless of your technological skills or viewing status.

5. Younger generations

Offer technology to young people and they are likely to use it, whether or not it is strictly 'necessary' to them. 2022,70%of 18-25 year olds “mostly” turned on subtitles while watching video content, not because they were hard of hearing, but because it was convenient. And many Tik Tok users took advantage of the app's TTS feature, which competes with Instagram.launched its TTS in 2021.One nowresearch with studentsfound that only 5% of respondents had a disability that required the use of assistive technology, but at least 18% of students considered any technology to be 'necessary'. Thing is, Gen Z uses TTS not just as an accessibility tool, but as a preference.

6. Readers with visual impairments or light sensitivity

Older adults aren't the only ones who want to avoid squinting at screens. Many people have mild visual impairments or are sensitive to light. For example, think of people with chronic migraines. Thanks to TTS, these users can be more productive on days when staring at screens feels like excruciating pain.

Actually,Advice on medical studiesthat exposure to light at night, particularly blue light from computer screens, has adverse health effects. Not only does it disrupt our internal clocks, but it can also increase the risk of cancer, diabetes, heart disease, and obesity. Text-to-speech offers users a safer way to consume written content without looking at a screen.

7. Foreign language students

Studies show that hearing another language helps students learn the new dialect. Text-to-speech can help with this.ReadSpeakeris an international TTS software company with 50+ languages ​​and 150+ voices, all based on native speakers.

With ReadSpeaker, foreign language learners can get a picture of pronunciation, cadence and accents. A particularly useful feature in this regard is the ability to highlight words as you read them, which can help students feel more confident when pronouncing new vocabulary.

8. Multilingual readers

New generations growing up in multilingual families may understand the language of their parents (grandparents) but may not feel fluent enough to read, write or speak it. This is common in many communities where the mother tongue is not taught in schools. For second and third generations who wish to maintain or strengthen ties with their home countries, ReadSpeaker can make articles, newspapers and other literature accessible and understandable through language.

9. People with severe speech impairments

A speech generating device (SGD), also known as a voice output communication aid (VOCA), is useful for those who have severe speech problems and would otherwise be unable to communicate verbally. Summarized under the term "Augmentative and Alternative Communication (AAC)", SGD and VOCA can now also be integrated into mobile devices such as smartphones.

Stephen Hawking, who suffered from ALS, and renowned film critic Roger Ebert were among the most well-known SGD users of TTS technology. So who uses TTS? Lots of people, for lots of different reasons. And if you're looking for a way to solve today's business challenges, TTS could be the technology for you.

For more information on ReadSpeaker's TTS services, see yourProductsÖFREQUENTLY ASKED QUESTIONS.

TTS technology for business

When ReadSpeaker AI started synthesizing speech in 1999, TTS was mainly used as an accessibility tool. Text-to-speech makes written content available on platforms for people with visual impairments, low literacy skills, cognitive disabilities, and other accessibility barriers. And while accessibility remains a core value ofReadSpeaker solutions,The rise of voice computing has led to a growing range of applications for TTS on all devices, especially in the enterprise.

Here are just some of the powerful business use cases for TTS in today's voice-enabled world:

• Conversational Interactive Voice Response (IVR)-Systeme,as in customer service call centers
• Voice Trading Applicationshow to shop on an amazon alexa device
• voice guidance and navigation tools,like gps map apps
• smart home devicesand other voice-enabled Internet of Things (IoT) tools
• freelance virtual assistantslike Apple's Siri, but for their own brand
• Experimental marketing and advertising solutions,like interactive voice ads on music streaming services or branded smart speaker apps
• video game development,with dynamic TTS runtime for accessibility features, scene prototyping and AI non-player characters
• Corporate training and marketing videoswhich allow creators to change voiceovers without tracking down the original speaker for ongoing recording sessions

It is likely that you have already experienced TTS in some or all of these examples. If you run a business, you may even have helped create a voice-first device or experience. With such widespread adoption, it's safe to say that TTS is here to stay. But it's not exactly a new technology.

Types of TTS technology, then and now

Mechanical attempts at synthetic speech date back to the 18th century. Electric synthetic speech has been around ever sinceHomer Dudley's Voder from the 1930s.But the first system that went directly from text to speech in Englisharrived in 1968,and was designed by Noriko Umeda and a team from the Japan Electrotechnical Laboratory.

Since then, researchers have developed a cascade of new TTS technologies, each working in different ways. You might ask, "How does text-to-speech work?" The answer depends on the TTS technology used. Here's a brief overview of the dominant forms of TTS, past and present, from early experiments to the latest AI features.

Formant synthesis and articulatory synthesis

Early TTS systems used rule-based technologies such as formant synthesis and articulatory synthesis, which achieved a similar result through slightly different strategies. Pioneering researchers recorded a speaker and extracted acoustic properties from this recorded speech: formants, qualities that define speech sounds in formant synthesis, and mode of articulation (nasal, plosive, vowel, etc.) in articulatory synthesis. They then programmed rules that modeled these parameters with a digital audio signal. This TTS was pretty robotic; These approaches inevitably abstract away much of the variation you find in human speech, things like pitch variation and accent, because they only allow programmers to write rules for a few parameters at a time. But formant synthesis isn't just a historical novelty: it's still used in the open-source TTS synthesizer.Ehablar OF,that synthesizes speechNVDA,one of the best free screen readers for Windows.

Diphonemsynthese

The next major development in TTS technology is called diphoneme synthesis, which was developed by researchers in the 1970s and was still widely used at the turn of the millennium. Diphone synthesis creates machine speech by mixing diphones, combinations of individual phoneme units, and the transitions from one phoneme to the next: not just the /c/ in the word cat, but the /c/ plus half of the next sound /ae/ . The researchers record between 3,000 and 5,000 individual diphones, which the system combines to form a coherent statement.

TTS diphone synthesis technology also includes software models that predict the duration and pitch of each diphone for the given input. When these two systems are superimposed, the system combines the signals from the diphones and then processes the signal to correct pitch and duration. The end result is synthetic speech that sounds more natural than formant synthesis produces, but it is far from perfect, and listeners can easily distinguish a human speaker from this synthetic speech.

Drive selection overview

In the 1990s, a new form of TTS technology took hold: Drive Select Synthesis, which is still ideal today for low-power TTS engines. When diphone synthesis has added the appropriate duration and pitch by a second processing system, unit selection synthesis skips this step: it starts with a large database of recorded speech (about 20 hours or more) and selects the sound bits that already have the duration and have pitch. Text input requires natural-sounding speech.

Unit selection synthesis yields human speech without much signal modification but is still artificially identifiable. During all these decades of development, computer processing power and available data storage increased rapidly. The stage was set for the next era of TTS technology, which, like much of today's computing age, relies on artificial intelligence to perform amazing predictions.

neural synthesis

Remember the deep neural networks we mentioned earlier? This is the technology that is driving the current advances in TTS technology and is key to the realistic results that are now possible. Like its predecessors, Neural TTS starts with voice recordings. This is an entry. The other is the text, the written script your host used to create those recordings. Feed this input to a deep neural network, and it learns the best possible association between a piece of text and its associated acoustic features.

Once the model is trained, it will be able to predict realistic sounds for new text: using a trained TTS neural model together with a vocoder trained on the same data, the system can produce speech similar to that of the original speaker is remarkably similar when exposed...to virtually any new text. This similarity between the source and the output is why neural TTS is sometimes referred to as "Cloning Voices”

There are all sorts of signal processing tricks you can use to alter the resulting synthesized voice so that it doesn't sound exactly like the source speaker. The most important fact to remember is that the best AI-generated TTS voices still start with a human speaker and TTS technology is becoming more and more human. Current research is resulting in TTS voices that speak with emotional expression, unique voices in multiple languages, and increasingly realistic audio quality.Discover the languages ​​and voices available with ReadSpeaker TTS.

It's probably more technical than you need, but it covers the basics of text-to-speech and then some. And if you still have questions, follow the links below.

To learn more about text-to-speech, help create your ownbrand voice,o Access to marketable productsVoice TTSin more than 30 languages,Contact ReadSpeaker today.