For product noise rating and for applied research relating to noise control and reduction, an acoustic laboratory is required. Many manufacturers have rooms set aside for the purpose of sound testing and evaluation; however, few of these could be considered as acoustical laboratories. The purpose of an acoustic laboratory is to obtain accurate assessments of noise by sufficiently accurate measurements. In acoustics much of the information can only be obtained by measurements.Laboratory rating tests are necessary to provide accurate measurements of absolute sound power output of equipment so that noise criteria for the installed equipment can be met reasonably. Applied research is concerned with identifying noise sources and characteristics for the purpose of reducing the noise produced. The physical nature of sound and the need for accuracy of measurements require a fundamental understanding of the measurement system and the facilities required.