Lambda SR1, Operation Manual, Page: 52 / 317

SR1 Operation Manual 52
© 2014 Stanford Research Systems
multiplied by the inverse of the frequency response of the EQ file.
When EQ is selected with chirp, the "Variable Sweep Rate" feature is enabled. Selecting Variable
Sweep Rate changes the chirp sweep rate to equalize the time domain amplitude in a chirp with variable
frequency domain amplitude.
For instance, the graph above shows the time response of a chirp weighted with the CCIR EQ curve.
The yellow trace was taken with Variable Sweep rate off, and the green with Variable Sweep Rate on.
Even though the two chirps have identical amplitudes in the frequency domain notice how more uniform
and how much lower the crest factor the variable sweep rate chirp has. The lower crest factor makes it
much more suitable waveform for audio testing.
The chirp waveform outputs a generator trigger once each cycle. Be sure to use generator
trigger as the analyzer trigger source when using the chirp waveform with the FFT analyzer.
Log-sine Chirp*
The log-sine chirp waveform is designed to work in combination the dual-channel FFT analyzer to make
impulse response measurements. The log-sine chirp waveform is a sinusoid whose frequency is swept in
a logarithmic fashion over the frequency span of its associated FFT analyzer. The log-sine chirp
waveform has a "pink" frequency roll off of 3 dB/oct.
The log-sine chirp waveform is synchronized to the settings of a particular FFT analyzer. If the resolution
or frequency span of that analyzer changes, the log-sine chirp waveform automatically reconfigures to