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Prabhas Pokharel contributed research and writing to this article.



For this post, we'd like to detail the different ways people and organizations are delivering audio content to mobile phones. Distributing audio content in this manner can help you reach new and increasingly mobile audiences. It can also be a great way to reach illiterate populations or others for whom written content is not suitable. 



There are many eays to deliver audio content to mobiles: Calling listeners, providing numbers for them to call, having mobile web- or app-accessible radio, or leveraging the radios that are included in many mobiles. This post will focus primarily on projects and tools that use phone calls, or the "voice channel," to share content.



Projects

There are quite a few projects that disseminate audio content using the voice channel:

• Freedom Fone, a Knight News Challenge winner, was deployed at two farm radio stations in Africa.
• Gaon ki Awaaz provides listeners in rural India with audio content twice a day in their native language.
• Avaaj Otalo lets farmers call in and listen to archived radio broadcasts in rural India.
• Geocell and Radio Greenwave in the country of Georgia make short broadcasts available to listeners if they dial a specified number.
• Listeners can call in to hear podcasts in the United States.
• In India, Bubbly allows content providers to upload messages that can be broadcast to a list of followers. Listeners can follow audio content from Bollywood celebrities.

How It's Being Done

Here's a basic overview of how voice-based technology is used to deliver audio content to a mobile audience. There are many other ways to share audio via data channels such as podcasts, audioblogging, mobile web radio, and apps. We'll revisit data channels in a later post.

There are many voice channel options available, including standard phone calls, call-in podcasts, IVR systems, self-hosted systems, and voice-based content management systems.

Humans answering phone calls
The simplest voice-based services can be provided by a team of operators who answer phone calls and provide information to callers. There is no need for users to go through complicated menus, or for automated voice processing. This makes these systems easy to use and install. Question Box is one example.

Call-in Podcasts
Podcasts are a very simple way to upload audio, and some services let listeners call in to listen to podcasts in select countries. The service Podlinez provides publishers a U.S. phone number that listeners can call. Bubbly is another example of a call-in podcast.

Simple IVR systems
Interactive Voice Response systems are commonly used to access audio information. Callers are prompted with menus, which they can navigate by pressing buttons on their phone keypad or by uttering short commands. Simple IVR menus can be built fairly easily:

• VoiceXML is a specification that is widely used to develop IVR menus. VoiceXML is a simple specification language like HTML or XML. In the same way HTML code is interpreted by a web browser to produce a webpage, a "VoiceXML browser" can interpret VoiceXML code to produce an interactive voice response system.
• In the U.S., hosted solutions like Bevocal cafe offer ways to get started with VoiceXML.
• VoxPilot VoxBuilder offers local numbers in many other countries. More providers are available at Developer.com.
• For diving into VoiceXML development, a great resource is World of VoiceXML.

Self-hosted systems
Another way of delivering voice-based audio content to a mobile audience is a self-hosted telephony system. There are a number of open-source platforms that provide code for many self-hosted telephony systems: Asterisk, Trixbox, and FreeSwitch. There are also many resources available for working with these tools:

• Asterisk has a dedicated documentation project. There are also sites that offer video tutorials, and many books have been written on the topic. There are also third party companies that will provide you with support services.
• Freeswitch has an extensive wiki for documentation. There are forums outside the main site and third-party support services are also available.
• Trixbox documentation is listed on the Trixbox wiki. Trixbox has a professional version that comes with support services.

Voice-based Content Management Systems
Finally, there are some voice-based content management systems in development, which aim to make voice-based telephony as easy to install as standard content management systems. One example is the aforementioned Freedom Fone.

What other resources would you add to this guide? Share them in the comments and we will update this post.

More Reading

How to Capture High Quality Video on Your Mobile Phone

Image by Andrew Michaels via Flickr