Audio
Music and other audio elements are excellent features for a website. They can also annoy your users very quickly. I absolutely hate when I am surfing the net to find some loud audio automatically being played. The worst part of the experience is that I have to go out of my way to shut it off. Most users will not even bother to mute the audio, as exiting the webpage will do the same effect. Websites with audio can provide a wonderful experience for the users, but can easily provide the opposite effect.
Audio Usability Issues
Starting Audio Automatically
I know you might think you have some strong reasons for starting some audio automatically. But why not let the user choose to decide if they would like to hear it? What about YouTube, you might ask. That is completely fine because the user expects YouTube to play audio when they click the link to the video. Another difference is that YouTube does not play audio on their home page, but allows you to follow links to videos. If you have ads with video on your website, make sure they do not start automatically. Please never play audio as soon as the user arrives on your website.
Sound Levels
If you decide to place audio or music on your website, then you should consider some things first. I would expect that users are much more irritated with loud audio than silent audio. What I mean is the audio you embed should have the ability to be really loud, but the volume should be set on like 30%. How annoying are those sound clips that when you turn up your speakers to 100% you can barely hear it? Volume is not something you can standardize. Users will have their volume on different levels, but it is far better to error on the video starting too quiet as opposed to bursting their eardrums. If they cannot hear it, they can just turn it up.
Hearing Impaired Users
There are people in the world that will never hear the sound of your website. If you have an important video for your website, you might want to consider writing the words out for them. Then, you can provide a link to the written text of the video. You might even want to create an option from them to turn on captions or subtitles. These users will be very thankful for you effort and will most likely tell their friends about your website.
While most websites do not include audio on their website, audio can benefit your users. It provides another unique way to connect with your users. However, you can easily commit some serious usability issues that would make users run away from your website and never look back. With audio, always think of it as being an opt-in strategy and not an opt-out process. Sometimes, we just do not feel like listening to the website. We just want to read the text and drink our coffee.