Over the past years, artificial intelligence has sneaked into the creative domain. Today, the buzz around it is undoubtedly deafening. We can expect creative AI’s impact, or “generative AI,” to grow in the coming years as the technology becomes more powerful.
In 2022, the global generative AI market size was estimated at USD 10.79 billion. Now it’s projected to hit around USD 118.06 billion by 2032, growing at a CAGR of 27.02% during the forecast period from 2023 to 2032.
However, generative AI isn’t about making creativity “quick and easy.” It’s about opening new ways of expressing yourself and helping creators find their authentic voices. Since we are moving toward a voice-driven world with the consumption of audio content and voice-based automated services, advancement in the field of AI and text-to-speech domain has given rise to speech synthesis or synthetic voices.
Your typical day probably includes all kinds of synthetic speech with the help of apps, smart speakers, and wireless headphones. But what is speech synthesis? This blog post will take a closer look at text-to-speech technology and discuss its pros and cons. We will also provide you with tips on choosing the right speech synthesizer. So, if you are interested in learning more about this technology, keep reading!
What is Speech Synthesis?
Speech synthesis, also known as text-to-speech (TTS), is the artificial production of human speech that sounds almost like a human voice but with more precision in pitch, speech, and tone.
Speech synthesizers simply take your written words and convert them into spoken language. The speech is usually produced using AI and deep learning. Often, it is used conversely with voice cloning as well.
Apps, smartphones, and even cars now have built-in TTS tools. Siri and Alexa are the perfect examples of TTS — they detect your voices and reply in kind, sometimes in ways that amaze us. Occasionally people confuse it with speech recognition, but the main difference is that speech recognition exploits the voice, whereas the latter produces the voice.
How Does Speech Synthesis Work?
Suppose you have a paragraph of written text and want your computer to speak that aloud. How does it going to happen? How can you hear the written words? Well, for that, there are three main steps involved:
- Text to Words
- Words to Phonemes
- Phonemes to Sound
Stage 01: Text To Words
Reading the text written in front of you sounds pretty easy, but it’s not trivial as it seems. The main problem is that the written text is ambiguous. The same written text has more than one meaning; therefore, you need to understand the exact meaning of the text or make a precise guess. So the first step in the speech synthesis process is reducing the “text ambiguity,” commonly known as “normalization” or pre-processing.
In pre-processing, the computer goes through the text and cleans it up to minimize the mistakes while reading the words aloud. What’s hard for a computer is to convert things like numbers, dates, time, abbreviations, symbols, currency symbols, etc., into words. Since we follow the context of what’s written and figure out the right pronunciation, computers can’t do so. Therefore, they use statistical probability techniques or neural networks to understand the right context and pronunciation.
Furthermore, pre-preprocessing handles the homographs. Homographs are words that often share the same pronunciation but have different spelling and meanings. For example, the term “sell” and “cell” has the same pronunciation. The sentence “I sell the flower” is quite problematic for a speech synthesizer. However, if the speech synthesizer understands the preceding text correctly by recognizing the spelling “I have a cell phone,” then it can have a precise idea that “I sell the pen” is likely correct.
Stage 02: Words to Phonemes
Once the speech synthesizer figures out the words that need to be spoken, the next step is to generate the speech sounds for those words. Every computer requires a huge alphabetical list of words and details to pronounce every word. And for each word, a computer would need an understanding of the phonemes that make up its sound.
What are Phonemes?
Phonemes are the atoms of spoken sound. These are the sound components from which you can make any spoken word. There are only 26 letters in the English alphabet, but over 40 phonemes because you can read the alphabet in multiple ways.
For example, “a” can be read differently, as in “pad” or “paid .” so instead of one phoneme per letter, there are phonemes for all the different letter sounds.
Every computer needs a huge alphabetical list of words and details which entails how to pronounce each word. They would need a list of the phonemes that make up the sound for each word. Once they figure out the words that need to be spoken, the speech synthesizer has to generate the sounds that make up these words.
Typically, if a computer has a dictionary of words and phonemes, it would simply read a word, look up in the list and read the corresponding phoneme. Nonetheless, this whole process is pretty hard. But there’s an alternate approach to it which involves breaking down the written words into graphemes—afterward— generating phonemes that relate to them with a simple set of rules. This approach enables the computer to read the words more precisely.
Stage 03: Phonemes to Sound
Until now, the computer has converted the text into a list of phonemes, but there is an issue: how do we find the basic phonemes the computer reads out when turning the text into speech? For that, there are three different approaches:
Using Recordings Of Phonemes In a Human Voice — Concatenative Synthesis
This technique generates new audible sounds by taking speeches from a huge database of audio voices. However, this approach isn’t scalable because whenever you need a unique style of speech, a new database is required, which is impossible.
Computer Generating the Phonemes Itself — Formant Synthesis
Formants are the 3-5 major resonant frequencies of sound that a human vocal chord generates and combines to make speech or singing sound. Formant speech synthesizers can even say words that don’t even exist or words they’ve never heard of.
Replicating the Human Voice Technique — Articulatory Synthesis
The most complex and least explored approach for generating sounds — articulatory synthesis makes a computer speaks by modeling the intricate human vocal tract and articulating the process occurring there.
The Wide-Ranging Applications Of Speech Synthesis
While technology advances, it’s hard to find out whether you’re listening to a simple recording or a speech synthesizer. Work your way through a typical day, and you might hear multiple recorded voices. There might be an alarm clock that wakes you up by speaking the time, or you read an ebook with a built-in narrator.
We created a list for you with the major applications of speech synthesis technology since plenty of business verticals could benefit from it:
Assisting Visually Impaired Persons
Speech synthesis is great for visually impaired persons. It empowers them to read from a screen to access written content by hearing it. Even if you don’t have any visual impairment, reading for a longer time on screen can still have significant visual stress. In such situations, TTS provides readers a break from staring at screens without interrupting their reading.
Speech synthesis is also an assistive technology for persons with speech impairments like dysarthria, mutism, or aphasia. It’s a lifesaver for those with trouble speaking but still want to communicate with others. Various apps and devices use TTS software to help them communicate.
Preparing Educational Material
Speech synthesizers are perfect for students having reading impairments like Dyslexia. Moreover, you can prepare audio lectures, audio blogs, and other language learning materials smoothly with speech synthesizers. Listening to material helps you focus, understand, and memorize things better than just reading them. Also, it enables you to multitask while you consume audio content.
Translating Multiple Languages
Since you can precisely control the synthesized speech, unlike human speech, producing an accurate rendition of the original text is easier. You can accurately translate your text into various languages with high-quality speech synthesizers while minimizing the chance of error-prone outputs and reducing long processing time.
Enhancing Navigation Systems
Siri and Google Voice Assistant are absolute examples of TTS software. They convert text-based directions into speech, making staying focused on the road while driving easier. Moreover, it helps people who lack good map reading skills or are unfamiliar with an area.
Offering Flexibility to Entertainment Industry
Whether it’s about dubbing an actor’s voice in post-production or bringing back the voice of a deceased actor, speech synthesis is a valuable technology for filmmakers and TV producers. Now there is no need to call back actors to the studio, again and again, to record a few lines. Neither voice-over artist is required to dub the actor’s voice in another language. Speech synthesizers are here to do all this work, saving resources and time.
Voice synthesis technology empowers advertisers to be more creative, helping them replicate any voice to obtain the perfect commercial and grab the audience’s attention. What’s more, advertisers use singing voice synthesis, a technology that supports more emotions in voice and can sing.
Video Content Creation
If you want to take your YouTube channel, Instagram, or TikTok account to the next level, give speech-to-text tools a shot. Let’s admit it: not everyone is a great speaker, but with speech synthesis, anyone can create professionally aesthetic videos. That, too, are easy to understand. Type your script, and the TTS software will convert the text into spoken words. Record your video and add the converted audio file to it.
However, with so many options available in the market, choosing and integrating the right speech synthesizer is quite hard. Here are a few tips for choosing the best speech synthesis system for your use case.
Tips To Choose The Best Speech Synthesis Software
Consider the following factors while choosing any speech synthesis software:
The accuracy of synthetic speech is high if it correctly pronounces words and phrases. While many TTS systems use rule-based methods for generating synthetic speech, the output might be prone to errors if rules aren’t applied correctly. So choose a system with high-quality algorithms tuned for the particular use case.
The major use of speech synthesis is for blind people. If it isn’t able to understand the text clearly or the speech output isn’t similar to the human voice, it’s not the right one.
Real-time Performance Rate
Another crucial factor to consider while choosing the right speech synthesis system is its ability to generate synthetic speech in real-time. Several TTS use pre-recorded speech units concatenated together to create synthetic speech. The system may have problems with the real-time generation of synthetic speech if the units are not aligned properly or if there aren’t enough resources available.
Many text-to-speech systems run only on specific platforms and devices. It limits their portability. Always choose a speech synthesizer that is designed to use on various devices.
Besides the performance, service availability and latency rate of the speech synthesis system affect its reliability. While you might tolerate waiting for Alexa to play the next song, businesses with mission-critical applications will be less likely to handle significant outages that could happen repeatedly.
Best Text-to-Speech Synthesizers — A Look at the Leading Players in the Speech Synthesis Industry
The rise of artificial intelligence has led to an incredibly broad range of text-to-speech generators. Numerous text-to-speech software available now, but finding the perfect one requires time and effort. So we went ahead and found the best ones that fit your business needs.
Here’s a list of the top 10 text-to-speech synthesizers:
Murf helps you add high-quality, natural-sounding AI voices for your projects while offering a complete toolkit for making voiceover videos. You can combine images, videos, and music, adjust timing, and more. Also, it lets you upload your recorded voiceovers with the custom soundtrack feature. You can get a free grammar assistant and add free background music to any video/audio.
If you want to create marketing content without having an in-house team, it’s one of the best TTS software. Synthesys offers you tens of AI avatars to play the spokesperson in your AI-generated videos. You can easily create explainer videos, commercials, training videos, audio instructions, podcasts, online courses, or tutorials.
Suppose you want single software for personal and professional use that gives you lifelike speech output. In that case, Natural Reader is a perfect choice. It is fairly simple to use. Just copy and paste the text or upload a document in any form, for instance, Docx, PPT, PDF, ePub, etc. and listen to it. Moreover, it has over a hundred natural-sounding voices in sixteen languages. It can read text from images using OCR technology.
Amazon Polly is a free text-to-speech app offered within Amazon’s suite of online tools. Besides converting basic documents and images to spoken text, it also provides you with the tools you need to create speech-enabled products and smart-talking applications.
You can Listen to articles, emails, PDFs, Word documents, and more using Speechify’s state-of-the-art text-to-speech technology. It converts your text into natural-sounding voices in more than 60 languages, including Spanish, Swedish, Portuguese, Dutch, Italian, and others. Aside from OCR software, Speechify also uses Speech Synthesis Markup Language (SSML) to mark language for speech synthesis programs.
By leveraging Amazon, Google, Microsoft, and IBM voices, Play.ht has become a frontrunner in the TTS industry. It generates realistic text-to-speech audio using an online AI voice generator and the best synthetic voices. With Play.ht you can instantly convert the text into more than 142 natural-sounding languages and accents.
With Speechelo, you can create videos with any software you like. Its usage is pretty simple — create a voiceover, download it in mp3 format and import it into the video editor. While supporting multiple languages, you will get a 100% human-sounding voiceover with all the expressions, which makes voiceovers more engaging for others.
With over a million audio files being generated on the platform, Resemble.ai is one of the most versatile AI voice generators out there. The Resemble Fill clones your voice and blends it with artificial intelligence-generated voices for a seamless audio experience. Using this AI voice generator, you can create ads, dialogue audio, and brand voices for assistants and IVR agents.
Descript is your go-to option if you are a podcaster or have a small business. Its features to edit, record, transcript, and share audio/video files are what sets it apart from other speech synthesis tools. Furthermore, it offers a free option to edit and screen record for a limited time.
Google Cloud text to speech
Google Cloud Text to Speech allows you to take advantage of 90+ WaveNet voices built on DeepMind’s groundbreaking research to bring about speech that truly closes the gap with human performance.
Moreover, you can convert text into more natural-hearing speech using an API powered by the best of Google’s AI technologies. With its widest voice collection, you can create an inimitable voice and represent your brand across all your customer touchpoints instead of using a typical voice used by other organizations.
The Future is Now: The Exciting Advantages of Speech Synthesis Technology
Already, digital voice interactions fuel the growth of new digital spaces like metaverse and augmented reality. But tech trends don’t dictate good business decisions. The benefits of new investments must be quick-paying—and—text-to-speech does! There are various advantages of speech synthesis covering everything from accessibility to user experience.
Creating speech content is pretty expensive and consumes too much time. Here, TTS software can help you. This software are great for making written content accessible through voice.
suppose you need to do a podcast and can’t afford the basic equipment. In this situation, you must write a creative script and let speech synthesis do the rest of the work. Speech synthesis software is affordable and can help you easily convert text into speech.
Broader and more Diverse Reach
TTS software is the ultimate way to go if we’re talking business. In case you need to extend the reach of your content and acquire new customers, who sometimes are too busy to read your content. Also, it comes in handy with publishing when you need to convert articles, stories, or books into audio.
Increased Web Presence
Speech synthesis offers increased web presence as websites with TTS technology attract some 774 million people globally with literacy issues and 285 million with visual impairments.
Enhanced User Experience
Most of you are more likely to return to a website where you had a smooth experience. While word of mouth is still the most important platform, having an alternative way to consume content online through speech synthesis enhances the user experience.
There’s no denying that speech synthesis technology is uncannily good and has become an integral part of our daily lives. Previously, the most realistic synthetic voices were created by recording audio of a human voice actor, splicing their speech back together like letters in a ransom note, and then combining these sounds to form new words. Currently, neural networks are trained using unsorted data of their target voices to generate raw audio from scratch of anyone who speaks.
The final results are smooth and more lifelike. Though the quality is not perfect when rolling straight out the machine, they’re only going to get better shortly.