It is not an easy task to evaluate instrument standards such as ANSI S1.4, IEC 651, IEC 804, and IEC 1672: Sound level meters, which is under development. Traditionally, proposed calibration procedures are tested with existing instruments from various manufacturers. Obtaining quantitative data to justify proposals on tolerances and to measure the combined effects of tolerances on the final instrument readings is extremely difficult. The above tasks can be done with relative ease with a computer emulation of virtual instruments. A sound level meter based on virtual instrumentation using the latest software technology, cost-effective data acquisition, control hardware, and a computer is presented. For manufacturers of acoustical instruments, a graphic designer interface also makes it possible to evaluate ``user-defined'' instrument systems with reduction in development time and costs.