This landmark paper by Angelo Farina discusses the benefits of the Log Sine Sweep (also known as Frequency Log Sweep or Log Chirp), one of the test signals available in SoundCheck.
A novel measurement technique of the transfer function of weakly not-linear, approximately time-invariant systems is presented. The method is implemented with low-cost instrumentation; it is based on an exponentially-swept sine signal. It is applicable to loudspeakers and other audio components, but also to room acoustics measurements. The paper presents theoretical description of the method and experimental verification in comparison with MLS.

Authors: Angelo Farina
Presented at the 108th AES Convention, Paris, 2000

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Distortion curves are conventionally plotted under the corresponding excitation frequency of the measured fundamental. Interpretation of results can be misleading due to the influence that the passband shape and amplitude irregularities of the fundamental response have on the distortion responses. By ‘amplitude normalizing’ the distortion responses to the measured fundamental response before plotting them at the excitation frequency, distortion graphs become easier to interpret for diagnostic purposes. In addition, the distortion curves become insensitive to room reflections in the measured responses.

Authors: Steve Temme
Presented at the 94th AES Convention, Berlin, 1993

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