An apparatus and method for producing colloidal silver. An interactive tool allows the advertiser to create an advertisement related to the trip items. In this embodiment, the different sets of spatial parameters are applied to synthesize an auditory scene comprising the different source signals. Kits for carrying out the assay method are also disclosed. The casing prevents leakage of unwanted electromagnetic waves from inside, is not affected by external electromagnetic waves, has small thickness, light weight, high strength and high rigidity, and has excellent contactability with a coating.