Virtual Instruments
(Continued from p. 1)

is in its ability to store the acquired data for whatever pro- cessing and display ("post-process- ing") is required; without today's super-fast CPUs and dirt-cheap memory and mass storage, such powerful tools would not be eco- nomically or physically possible. And the system is powerful enough to do post-processing practically in real time.

In spite of the great hardware capabilities that are available, Temme is a strong advocate of keeping things simple and user- friendly. His products are contin- ually evolving to meet this goal. The virtual instruments look and act like the ones you are used to, and familiar sounds and standard Windows interfaces are used for control and user feedback. All the PC's available I/Os can be used for test control (eg. a footswitch) and status (eg. failure buzzer).

A basic swept-sine technique is used (though it takes only a few seconds) rather thana multi-tone tech- nique; multiple tones can mask harmonics or IM. Noise should be used to measure overall response only; it won't produce accurate distortion results. Using FFT processing can reduce noise to below harmonic levels so that no data is lost. Temme pointed out that, since test frequencies are harmonically related they don't have to match the FFT lines exactly, and test frequency and phase can be calculated automati- cally.

Temme showed his
Sequence Editor which can produce custom test proce- dures from a library of stan- dard "modules". End-to-end calibrations for mic or speaker testing are also

(Continues p. 3)