Lambda SR1, Operation Manual, Page: 102 / 317

SR1 Operation Manual 102
© 2014 Stanford Research Systems
2.3.10 Multitone Panel
Multitone Testing is a relatively new technique (compared to traditional audio measurements, many of
which have their roots in the 1920s and 1930s) which enables testing of multiple audio parameters using
the information contained in the FFT of a short record of audio data. By using a stimulus signal which
contains discrete tones at only few of the bin frequencies of the FFT, the Multitone analzyer can
examine the amplitude of bins in the FFT which correspond to tones in the original signal (frequency
response), harmonics of tones in the original signal (THD and THD+N), intermodulation products of tones
in the original signal (IMD) and finally bins where none of the above are present (Noise). All these
measurements can be made
simultaneously , on the data found in a single FFT, instead of by making
multiple laborious swept measurements.
Setting up multitone testing on SR1 involves configuring the generator and the analyzer. Details of the
analyzer configuration are discussed in the
MultiTone Analyzer section. The MultiTone configuration
panel discussed here is concerned with details of the generator configuration. Once the tone placement,
signal length, etc. are configured on the Multitone Configuration panel the user needs to select the
MultiTone waveform on the analog or digital audio generator in order to begin generation of the multitone
stimulus signal.
Unlike many other audio analyzers, SR1 does not require the user to employ a offline
program to calculate a multitone stimulus signal and then load it into an arbitrary waveform
generator. Once the multitone waveform is running on SR1, any changes to the waveform
made on the Multitone configuration panel are immediately reflected in the generator output.
The Multitone Configuration Panel
Generator
The Domain control selects whether the Analog or Digital generator will be used. For the Analog
Generator, a choice of fixed sampling rates (512 kHz, 128 kHz, and 64 kHz) as well as variable rates
(digital audio output sampling (OSR) and input sampling rate (ISR)) can be selected using the "Fs"