ADDA

This is the actual measuring section of WinMF. From here specific measuring signals are played back, fed into an arbitrary system and a system response is recorded.

ADDA is the acronym for analogue->digital and digital->analogue conversion of signals. The measuring signal is stored on a computer in digital form and is usually transformed to the analogue domain by a frontend. This analogue signal is then amplified for example, played back by a loudspeaker and recorded by a microphone, amplified again, converted from analogue to digital in the frontend and then recorded. Also purely electrical measurements are possible, with filter circuits for example, as well as measurements of purely digital signal paths through the digital inputs and outputs, although in this case there is no actual AD/DA conversion happening.

AD & DA is the most general sort of measurement. In this case an arbitrary signal is played back while the system response is being recorded. The result of the measurement is now to be processed and evaluated.

An important class of measurements consists of the (non-linear) distortion measurement functions. Sine- or multisine signals are used for excitation. These measurements analyse, which spectral components are added by the system under test, for example harmonic distortion (multiples of the excited frequency), intermodulation distortion (for example sum and difference of excited frequencies) or noise components. This group of measurements comprises Harmonic distortion, Harmonic distortion (f), Max.SPL and Multisine distortion.

Another large group of functions are the frequency response measurements, which use broadband signals, mostly sweeps, for excitation. In any case a reference measurement is necessary, because it's not the recorded signal itself that is of interest, but the alteration of the signal by the system under test, and thereof both the time characteristics and the linear distortion (frequency response). As part of the post-processing after the measurement, the result is automatically compared to the reference measurement (division by the reference) and displayed correspondingly. The most basic measurement in this group is Frequency response; then there is LS sensitivity, extended by some parameters specific to loudspeakers and microphones, as well as Polar response, creating sets of measurements in different directions for the representation of spatial transfer characteristics.

The Impedance measurement is similar to frequency response measurements; through a shunt resistor the complex ratio of voltage and current over frequency is measured at the device under test (e.g. a passive loudspeaker).