Sorry you had a bad experience with an ad. There should be absolutely no auto-play audio ads showing up on BYC. I've forwarded this along to our ad team to see if they can track it down and find out how it got on the site. Unfortunately it's the nature of the beast with online advertising that sometimes this stuff sneaks through, but we try very hard to not have it happen.
We try VERY hard to find chicken only advertising, but it's very hard to find enough advertisers that are interested in sponsoring a site like BYC. When that happens we need to turn to third parties (like Google AdSense) to supply the ads, and unfortunately we have much less control over what ads they display.
With that said, we're always working very hard to have related and appropriate ads on BYC, so if any member sees an ad that is inappropriate (compared to other sites on the web like Cnn.com Yahoo, etc. please let us know!
If you see this ad again, please take a screenshot so we can more quickly find it and remove it.