This standard gives the characteristics to be specified, performance requirements and the relevant methods of measurement for electromechanical volume indicators. The concept of "volume" is a practical way of assigning a numerical value to the magnitude of electrical speech and music programme signals. Since the response of the meter movement of such an indicator to the rapidly varying programme voltage is greatly dependent upon its dynamic characteristics, a standard for volume measurements shall therefore include a specification of these characteristics. The term "vu" (pronounced "vee-you" and written with lower case letters) is used to express volume in terms of vu above or below a specified reference level. This standard does not deal with peak programme level meters which are the subject of IEC 268-10.