Portable programmable calculator control of acoustic analyzer
Michael Brack · The Journal of the Acoustical Society of America · 1982
The recent introduction of the Hewlett-Packard Interface Loop (HPIL) has provided the means for interfacing the Ivie IE-30A 1/3-octave, real-time analyzer to the HP-41C programmable calculator resulting in a small portable system for detailed spectrum analysis in the field. A battery-powered interface is described which, in conjunction with the HP-IL converter, allows the HP-41C to read in the 1/3-octave or octave band spectrum to its memory with 0.2-dB resolution over a 50-dB dynamic range. The weighted level from the SLM portion can also be read into memory with about 0.5-dB resolution. Some of the programs developed for this system are described. These include a program to average spectra for use in determining the space-average SPL in a room from a moving microphone, which can then be printed out, stored to memory, magnetic card, or cassette for use in noise reduction, equalization or other calculations. Machine language programming of the HP-41C will also be discussed for use in speeding up data manipulations by a factor of 10 to 50 times over that of normal user code.