How is it possible to use aural style sheets on el

Just searched the Net and came up with the following codes..When I run them on Firefox4 and Safari, I don't seem to hear anything..How can I fix this?

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
@media aural {
h1, h2, h3, 
h4, h5, h6    { voice-family: paul, male; stress: 20; richness: 90 }
h1            { pitch: x-low; pitch-range: 90 }
h2            { pitch: x-low; pitch-range: 80 }
h3            { pitch: low; pitch-range: 70 }
h4            { pitch: medium; pitch-range: 60 }
h5            { pitch: medium; pitch-range: 50 }
h6            { pitch: medium; pitch-range: 40 }
li, dt, dd    { pitch: medium; richness: 60 }
 dt            { stress: 80 }
pre, code, tt { pitch: medium; pitch-range: 0; stress: 0; richness: 80 }
em            { pitch: medium; pitch-range: 60; stress: 60; richness: 50 }
strong        { pitch: medium; pitch-range: 60; stress: 90; richness: 90 }
dfn           { pitch: high; pitch-range: 60; stress: 60 }
s, strike     { richness: 0 }
i             { pitch: medium; pitch-range: 60; stress: 60; richness: 50 }
b             { pitch: medium; pitch-range: 60; stress: 90; richness: 90 }
u             { richness: 0 }
 a:link        { voice-family: harry, male }
 a:visited     { voice-family: betty, female }
a:active      { voice-family: betty, female; pitch-range: 80; pitch: x-high }
}
</style>
</head>

<body>
<p id="a" class="heidi">Testing</p>
 <p id="b" class="peter">Testingb</p>
 <h2>Heading2</h2>
</body>
<html>

Aural style sheets are for screen readers to read (hence the aural media type you see in the beginning of the style sheet), not for browsers to render. That's why your browser doesn't say anything.

They're accessibility tools for people with visual impairments, who need to rely on hearing rather than vision to peruse Web sites.

Aural style sheets are described in the CSS2.1 spec, but have been superseded by the CSS3 Speech Module. It is not known what kind of support exists for either specification, though, as most screen readers in use simply read off what a browser renders and displays.