  We propose a new family of test signals for acoustic measurements such as
impulse response, nonlinearity, and the effects of background noise. The
proposed family complements difficulties in existing families, the Swept-Sine
(SS), pseudo-random noise such as the maximum length sequence (MLS). The
proposed family uses the frequency domain variant of the Velvet noise (FVN) as
its building block. An FVN is an impulse response of an all-pass filter and
yields the unit impulse when convolved with the time-reversed version of
itself. In this respect, FVN is a member of the time-stretched pulse (TSP) in
the broadest sense. The high degree of freedom in designing an FVN opens a vast
range of applications in acoustic measurement. We introduce the following
applications and their specific procedures, among other possibilities. They are
as follows. a) Spectrum shaping adaptive to background noise. b) Simultaneous
measurement of impulse responses of multiple acoustic paths. d) Simultaneous
measurement of linear and nonlinear components of an acoustic path. e)
Automatic procedure for time axis alignment of the source and the receiver when
they are using independent clocks in acoustic impulse response measurement. We
implemented a reference measurement tool equipped with all these procedures.
The MATLAB source code and related materials are open-sourced and placed in a
GitHub repository.
