Perhaps the most unique trademark is one for sound

Perhaps the most unique trademark is one for sound. Certain sounds are associated with products or services and thus can be trademarked. A classic example is the bonging noise used on the Law and Order television show. When a person hears the noise, they immediately associate it with the show. Obviously, the issue of whether something can be trademarked is a complex issue. You cannot just walk around trademarking various sounds and such. The Patent and Trademark Office wants to see some practical application in commerce that is known by people. That being said, do not assume that you cant trademark something just because it is not a logo.