Hi nauna,
Refer below sample.
HTML
<audio controls id="buzz" runat="server" type="audio/mp3" />
Code
C#
protected void Page_Load(object sender, EventArgs e)
{
buzz.Attributes.Add("autoplay", "autoplay");
buzz.Attributes["src"] = "Test.mp3";
}
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handle Me.Load
buzz.Attributes.Add("autoplay", "autoplay")
buzz.Attributes("src") = "Test.mp3"
End Sub