Web accessibility is the practice and methods of making web sites accessible and usable by people with disabilities. There are a variety of web accessibility considerations, including visual, hearing, physical, and mental accessibility. The topic is such a large one that it is necessary to focus on a particular aspect of accessibility, which is why this article only addresses accessibility for the hearing impaired.

One of the most straightforward ways to make multimedia content accessible is to add captions to audio or video tracks. This method does not require changes of design/layout, as it adds the accessible content directly into the current media.

There are many tools that can be used to create captions. They can be added in a video editing program, but the process can be time-consuming and unless editing the movie twice is an option, leaves only the captioned version as the final product. A better option is to use a technology built directly into QuickTime video: text tracks. Text tracks can be created by hand, or with a tool such as MAGpie, which creates SMIL presentations from your QuickTime video. Regardless of what tool is used, an effort must be made to ensure that the captions are synchronized with the media.

"D" links (descriptive or definition links) are often used as a simple and quick way to add accessible information to complex content. The most common method to employ "d" links is to add the letter "D" immediately following a media object, and then to create a hyperlink from the "D" to a text-only page. "D" links are often used as a text equivalent for users with visual disabilities as well, making them a good option for reaching as many users as possible. 

D
A typical "D" link placed immediately following the media object for which it provides information.

"D" links require no additional multimedia skills, beyond the knowledge of HTML or a web page creation tool such as Dreamweaver. The pages they link to should not have any graphical content and only the text that describes the content, and, if appropriate, a transcript of the dialog contained in the media. A transcript should include information about whether or not music is playing, as well as any sound effects that take place. If there is more than one speaker in the media, such as a narrator or interaction between multiple people, each speaker should be identified immediately preceding the dialog attributed to them.

One last aspect of hearing accessibility that should be considered is audio cues. Interactive content can take advantage of both the senses of sight and sound, but a site that relies on only one sense for giving feedback to the user will be inherently inaccessible. Navigation of a site should not rely on audio cues, such as rollover sounds, in order for the user to find their way around. A combination of visual and auditory feedback should always be provided when interactive content of this nature is employed.

By keeping the concept of web accessibility in mind from the beginning of the design process, web designers and content creators will have an easier time making their content accessible to as many users as possible and avoid time-consuming and expensive updates at a later date.

MAGpie -
http://ncam.wgbh.org/webaccess/magpie/

QuickTime Text Tracks -
http://www.apple.com/quicktime/tools_tips/tutorials/texttracks.html

Macromedia - Creating D links in Dreamweaver
http://www.trainingcafe.com/macromedia/accessibility/techniquesmx.asp?offset=7

Section 508 - Goverment standards on acessibility
http://section508.gov/

World Wide Web Consortium (W3C) - Accessibility guidelines
http://www.w3.org/TR/WAI-WEBCONTENT/

Robin Martin
SDSU Educational Technology