Testing and validation are essential steps in the development of software platforms designed to emulate hardware components. Given that modern sound level meters rely heavily on digital signal processing for sound analysis, it seems reasonable to expect that results of equal or greater accuracy can be obtained on platforms computers. Requirements for precision measuring instruments are specified in the international standard IEC 61672-2003 – Electroacoustics – Sound level meters. The standard applies to stand-alone or multi-component analog and digital hardware systems, only briefly mentioning computer software as a provisional part of the instrument for display of results and limited manipulation of data. On the other hand, modern multi-channel digital systems provide means of storing recorded waveforms on a PC hard drive, thus relying entirely on dedicated software for all subsequent processing and analysis. Once integrated with hardware into a complete sound measuring instrument, such computer software becomes subject to compliance with international standards calling for model evaluation testing and periodic testing. The measuring instrument includes several components used for data acquisition, manipulation and analysis. An acoustic transducer (usually a condenser microphone), a signal conditioner, and an analog-to-digital converter are used to first convert the sampled analog signal into electrical voltage and then into its binary representation. Shelton [ ] recognizes this part of the instrument as the real-time layer where the instrument's resources are dedicated to particular functions 100% of the time. Once the signal has been sampled in real time, it is transmitted to the block-oriented system. .... middle of paper ...... were observed throughout most of the tests. This was not the case for other common wavefile sampling rates (44.1 kHz, 51.2 kHz) because the nominal frequencies of the test signal did not satisfy the periodicity condition. This problem is recognized in the field of audio measurement and documented in Lund's work and in IEC/TR 602680-18Sound System Equipment - Peak Program Level Meters - Guide for Digital Audio Level Meter. However, the topic has not been covered in detail since level monitoring in music and audio domains usually involves wideband signals as audio input. Recommendations are given to exclude problematic “exceptional” testing frequencies from the overall results. This approach cannot be translated into model evaluation testing for sound measuring instruments, because these critical frequencies are the starting point for the majority of electrical testing..