Just for my blog posts.. is there anything wrong with that? Don't know what you are talking about, sorry.
it would only effect on loading of page it would probably slow the page load of your blog other than that i dont see anything wrong why not to put audio to your blog
It is a waste of time and will slow your blog down. Many people do not even keep their speakers on and a lot of visitors will not want to wait for the audio to load. I am one who is stuck on dial-up and I would shut the page down instead of waiting for it to load.
If you regularly place audio in your blog, then you should look into podcast distribution for better marketing. It's a different audience, and you'll need to define "effectve" before you can decide whether or not it is achieving your goals. As for advertising, people who download podcasts generally use a syndication program, which cuts our all of your text links and banner ads. You can recoup this through audio/visual ads, but these markets generally require a large audience before they'll accept you into their programs. There are some smaller advertisers which will accept you, but you would be better off focusing on building your audience first.