Every project is different and every source for material is different, so to obtain voice clips and for them to be in the correct format will likely take some work. It isn't very hard, but it may take a bit of time depending on the source material and the number of word files you want to play.

First Try - Do Recordings Exist for Your Dialog?

Before generating custom dialog, does dialog exist somewhere already recorded? Probably not for specific texts but for simple words and phrases, yes there are websites that offer pre-recorded sounds. The sites may not always be on the Internet and it is likely the files need conversion to microcontroller-friendly format but it will save you time.

Here are sources for pre-recorded dialog that we have found and the licensing terms:

• Aspect - Pre-Recorded Audio: A wide variety of spoken words and phrases in American male english. Numbers, alphabet, much more. LGPL license.
• https://freesound.org/ has a large number of license free sounds.
• An Internet search may find additional resources for pre-recorded sounds.
• If you are looking to read numbers, this tutorial has pre-recorded numbers for you. See this page for more details.

Custom Voice Files

Method 1: Record Your Own Voice

A number of programs allow you to record your voice on your PC/Mac/Linux machine.

For all platforms: you may download and record audio with the free Audacity program.

You will want a "script" your phrases: write down the words you will want to play in your project. Then you or your voice person will speak each of the phrases one at a time with some space between words (or record each word as its own sound file which may save some edit time). 

You can also record sound effects, holiday sounds, etc. this way.

Method 2: Using Machine Generated Voice (text-to-speech)

While computers can generate voices, it can get convoluted, so we'll use the power of the web to use some websites to generate text to speech. Different services support different speakers (male/female) and languages.

Note that Adafruit does not endorse any 3rd party site, sometimes they restrict use or the site disappears, in such a case, go to another or use a search engine to find "Free text to speech mp3".

IBM BlueMix Text to Speech

The IBM speech engine is accessible at this web site. You can type in words, phrases, sentences and more and save the result as an MP3 file. Different speakers and different languages are supported.

See the example of how to use this on the next page.

NaturalReaders

This web site says it allows for 20 minutes of free speech conversion to MP3. 

fromtexttospeech.com

Another Text to Speech engine available here, works well, check out male voice John.

Text 2 speech .org

A basic site that has US and Indian voices and you can download in WAV and MP3.

Amazon Polly

This service charges a very small fee per character but you can use the recorded audio anyway you want.