Specifications

EAW Smaart 6 Operation Manual Concepts, Glossary, and Bibliography

2.1.8 Impulse Response

An impulse response is the response of a system under test (SUT) to an impulsive stimulus.

The SUT could be an electronic device, a sound system and/or an acoustical environment.

In Smaart the impulse response is the time-domain representation of the system’s transfer

function, or system identification. For our purposes, this means a signal that describes

the changes a known test signal undergoes as it passes through the SUT. The impulse

response contains a wealth of information about the SUT including its propagation delay

and frequency response. For an acoustical system, it also contains information about

reflections, reverberation, and decay.

NOTE: It is actually possible to use the impulse response of a room/system as a filter

to convolve a dry signal, such as speech or music, and hear exactly what it

would sound like if played through that same system in that room and heard at

the measurement position.

2.1.9 The Transfer Function

All frequency response (Phase and Magnitude) and impulse response data in Smaart 6

rely on a mathematical calculation called a transfer function. The transfer function

compares a reference signal to a measurement signal, typically the input and output of

a device/system under test (DUT/SUT), such as an equalizer, sound system, or room.

Smaart 6 uses the transfer function calculation in both Frequency Response and Im-

pulse Response measurements. Transfer function calculations are always performed in

the frequency domain using FFT data. The results of the calculation are displayed in

either the frequency or time domain, depending on Smaart 6’s display mode.

The Frequency Response display plots transfer function results in the frequency domain

to show the magnitude and phase of the SUT. In Impulse mode, Smaart 6 calculates the

transfer function using data from very long FFTs, then transforms the result back into

the time domain to show the impulse response of the SUT. These two types of Frequency

Response measurements are complementary.

The reference and measurement signals must be aligned in time to obtain a valid fre-

quency response measurement. The impulse response measurement is used to find the

delay time between the two input signals.