I spent a summer building, testing, and assisting with designs on small vibrators, AMA. By testing, I mean that I performed a number of experiments on materials, motors, and variable resistors.
edit 3: I think the most important thing you can take out of this is that if you are to buy sex toys, please do some research and go to a shop where the staff is knowledgeable. This is important so that you can learn about the material the vibrator is made of, and get to hear how loud the vibrator actually is.
edit 2 After being on reddit's front page, I feel like I understand Kanye West a little more.
That was a joke
edit: Going to bed now, I will answer more questions tomorrow. I sent the mods some evidence and am awaiting a response.