最近发现语音验证码越来越流行，比如有次在注册Gmail邮箱看到过，还有msn页面也有语音验证码，还有国外一些网站等。
花时间研究了下，语音验证码主要跟一般验证码的区别就在于如何让验证码播放。本文语音验证码原理：从服务器生成验证码，
并保存到cookie中（getcode.aspx.cs）,当点收听验证码的时候，调用javascirpt操作（这里使用jquery）cookie读取验证码,
然后把验证码传到codevoice.aspx页，然后按顺序把验证码合成生成一个mp3文件，最后把这个文件传入Flash中播放，
你将收听的声音为：“当前验证码是5678请输入”。这个原理也是大部分网站使用的语音验证码原理类似。
源码下载:下载 （请使用VS2008 SP1或VS2010打开）
页面上放置验证码图片页面代码
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<form id="form1" runat="server">   
    <div>   
     <input  type="text" name="txtCode" id="txtCode" maxlength="8"  />   
<img onclick="this.src='getcode.aspx';" src="getcode.aspx" mce_src="getcode.aspx" align="absmiddle" style="cursor: pointer" mce_style="cursor: pointer" alt="看不清楚，换一张" title="看不清楚，换一张" />   
<img id="imgRead" src="image/maintb.gif" mce_src="image/maintb.gif" align="absmiddle" style="cursor: pointer" mce_style="cursor: pointer" alt="收听验证码" title="收听验证码" onclick="playvoice('player');" />   
<span id="player"></span>    
    </div>   
    </form>  
<form id="form1" runat="server">
    <div>
     <input  type="text" name="txtCode" id="txtCode" maxlength="8"  />
<img onclick="this.src='getcode.aspx';" src="getcode.aspx" mce_src="getcode.aspx" align="absmiddle" style="cursor: pointer" mce_style="cursor: pointer" alt="看不清楚，换一张" title="看不清楚，换一张" />
<img id="imgRead" src="image/maintb.gif" mce_src="image/maintb.gif" align="absmiddle" style="cursor: pointer" mce_style="cursor: pointer" alt="收听验证码" title="收听验证码" onclick="playvoice('player');" />
<span id="player"></span>
    </div>
    </form>


点收听验证码时调用的js函数如下:
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function playvoice(id) {   
    var voiceid = document.getElementById(id);   
    var voicecode = $.cookie('ValidateCode');   
    voiceid.innerHTML = "<embed id='sound_play' name='sound_play' src="sound_play.swf?" + (new Date().getTime()) + "" mce_src="sound_play.swf?" + (new Date().getTime()) + ""    
FlashVars='isPlay=1&url=codevoice.aspx&code=" + voicecode + "' width='0' height='0' allowScriptaccess='always'    
ype='application/x-shockwave-flash' pluginspage='http://www.macromedia.com/go/getflashplayer' /></embed>";   
}  
function playvoice(id) {
     var voiceid = document.getElementById(id);
     var voicecode = $.cookie('ValidateCode');
     voiceid.innerHTML = "<embed id='sound_play' name='sound_play' src="sound_play.swf?" + (new Date().getTime()) + "" mce_src="sound_play.swf?" + (new Date().getTime()) + ""
FlashVars='isPlay=1&url=codevoice.aspx&code=" + voicecode + "' width='0' height='0' allowScriptAccess='always'
type='application/x-shockwave-flash' pluginspage='http://www.macromedia.com/go/getflashplayer' /></embed>";
}


其中$.cookie('ValidateCode')是读取cookie验证码，这里使用了一个jquery操作cookie插件

生成mp3页面代码如下：
     //读取验证码生成mp3，这里包括头部begin.mp3和尾部end.mp3
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Response.ContentType = "audio/mpeg";   
           Response.WriteFile("sound/begin.mp3");   
           string checkCode = HttpContext.Current.Request.QueryString["code"].ToString();// string checkCode ="8888";   
           if (checkCode.Length > 0)   
               for (int i = 0; i < checkCode.Length; i++)   
               {   
                   Response.WriteFile("sound/"+checkCode[i] + ".mp3");   
               }   
           Response.WriteFile("sound/end.mp3");  
Response.ContentType = "audio/mpeg";
            Response.WriteFile("sound/begin.mp3");
            string checkCode = HttpContext.Current.Request.QueryString["code"].ToString();// string checkCode ="8888";
            if (checkCode.Length > 0)
                for (int i = 0; i < checkCode.Length; i++)
                {
                    Response.WriteFile("sound/"+checkCode[i] + ".mp3");
                }
            Response.WriteFile("sound/end.mp3");
            

【本文作者分别在cnblogs,csdn，http://www.Ajaxcn.net同步发布，转载请保留此说明】
flash播放代码主要在第一帧关键帧右击动作，插入以下代码根据传入的播放数字mp3地址

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var mysound = new Sound();   
var mysong = url;   
var isPlay = 1;   
var intnum:Number = setInterval(playSong, 500);   
function playSong() {   
if (isPlay == 1) {   
  mysound.loadSound(mysong+"?code="+code, true);   
  mysound.start();   
  clearInterval(intnum);   
  isPlay = 0;   
}   
}