Earlier quoted context omitted.
Just enable click-to-play in chrome, on media plugins. Sound only ever really auto-plays from flash ads and such (though these days its possible with HTML5 and this likely won't stop such audio/video). Its an extra click and can make some sites a bit more difficult (e.g. beatport, tries to hide its flash so you cant click it to enable it), but it works for me.
Click-to-play on plugins often breaks sites that use Flash ads as overlays. The ads often have the "close this ad" in the Flash code itself, making it impossible to kill the ad layer without activating the plugin. (In my more cynical moments, I wonder whether this behavior is by design.)
Use the context menu. There is an option to "hide" (delete) the ad there.
Another option is this bookmarklet (only works if the element that should be deleted isn't in an iframe):
javascript:(function(){var e=document.body.style.cursor;document.body.style.cursor="crosshair";var t=document.createElement("div");var n="border:1px solid #3280FF;background-color:rgba(50,128,255,0.5);position:absolute;z-index:2147483647;display:none;";var r="pointer-events:none;";var i="transition:width 60ms,height 60ms,left 60ms,top 60ms;";n+=r+"-webkit-"+r+"-moz-"+r;n+=i+"-webkit-"+i+"-moz-"+i;t.setAttribute("style",n);document.body.appendChild(t);var s=null;var o=function(e){var n=e.target;if(n!==s&&n.parentNode){var r=n.getBoundingClientRect();var i=document.documentElement;var o=document.body;var u=i.clientTop||o.clientTop||0;var a=i.clientLeft||o.clientLeft||0;var f=window.pageYOffset||i.scrollTop||o.scrollTop;var l=window.pageXOffset||i.scrollLeft||o.scrollLeft;var c=l-a+r.left-1;var h=f-u+r.top-1;t.style.display="block";t.style.left=c+"px";t.style.top=h+"px";t.style.width=r.width+"px";t.style.height=r.height+"px";s=n}};var u=function(n){document.body.style.cursor=e;if(n.target.parentNode)n.target.parentNode.removeChild(n.target);if(t.parentNode)t.parentNode.removeChild(t);window.removeEventListener("click",u,false);window.removeEventListener("mouseover",o,false);n.stopPropagation();n.preventDefault()};window.addEventListener("mouseover",o,false);window.addEventListener("click",u,false)})();void(0)