Abstract:

The design of a relatively low-cost Type 2 pocket-size sound-level meter with an embedded 8-bit microcontroller is described. The key design goal was to provide 110 dB of dynamic range without the need for user-controlled range switching. The miniature instrument meets all the current ANSI SI.4-1983 (R 1990) and IEC 651 (1979) sound-level meter standards. Relevant features in the future IEC 1672 sound level meter standard, such as level linearity, tone-burst response, over-range and under-range indication, measurement accuracy, and resolution are reviewed. Due to judicious separation of the functions performed by analog and digital hardware and software, the wide dynamic range is implemented with only 8 bits of A--D conversion. Extensive type testing confirmed that the instrument can satisfy the requirements of the standards over the required temperature range. [Work supported by Etymotic Research, Elk Grove Village, IL.]