07-08-2012, 04:56 PM
REVERBERATION MORPHING USING CEPSTRUM DECOMPOSITION
[attachment=30462]
ABSTRACT
Reverberation morphing from an impulse response is an
inevitable 3D-audio technology as well as reverberation
rendering for an immersive communication network. This
paper proposes a method for reverberation morphing by
relocating the poles and zeros of the transfer function. It
assumes that the distance of the pole/zero locations from
the unit circle in the z-plane represents the reverberation
condition for the transfer function. Exponential timewindowing
moves the minimum-phase zeros, while the
pole/zero relocation for the all-pass part is possible by the
windowing after causal and non-causal cepstrum decomposition.
We confirmed that the reverberation effects on
the frequency response rendered by the proposing method
were similar to those for recorded impulse responses in a
variable reverberation room. This morphing is also applied
to stable inverse filtering in a reverberant space.
INTRODUCTION
An immersive communication system requires rendering
of auditory events including 3-D spatial sound to enable
effective collaboration through an interactive sound field
network [1-3]. Rendering and morphing of room reverberation
are crucial technology of auditory events modeling
in virtual acoustics. This paper describes a 3D-sound
morphing by reverberation control using cepstrum decomposition.
Reverberators have been investigated as an effective
tool for sound recording and reproducing since many
years ago[4]. However reverberators that naturally sound
such as real-room reverberation are still under study. Tohyama
et al.[5] proposed a new method for generating an
impulse response which represents reverberation characteristics
based on superposition of free-oscillations whose
frequencies are determined based on the modal statisitics.
Modification of the Magnitude Response
The transfer function can be decomposed into the minimum-
phase and all-pass components. Figure 3 is a sample
of impulse response (Fig.3 (a)) with the decomposition
into the minimum-phase (3(b)) and all-pass (3©) components
in terms of poles and zeros. Relocating the poles
and zeros as illustrated in Figs 3(b) and 3©, the magnitude
and phase can be controlled.
MORPHING OF ROOM REVERBERATION
Let' s take the example shown in Fig.2. Figure 7 presents
the minimum-phase magnitude and all-pass phase responses
after the morphing by exponential timewindowing
with a negative exponent. We can confirm
similar effect to Figs. 4 and 6 on the minimum-phase and
all-pass components.
SUMMARY
We have described a method for reverberation morphing
based on relocating the poles and zeros of the transfer
function. Different from the modal theory, we assumed
that the distance of the pole/zero locations from the unit
circle in the z-plane represented the reverberation condition
for the transfer function. The proposed method can be
performed separately; by exponential time-windowing for
the minimum-phase part, and the same windowing for the
non-minimum components after causal and non-causal
cepstrum decomposition.
[attachment=30462]
ABSTRACT
Reverberation morphing from an impulse response is an
inevitable 3D-audio technology as well as reverberation
rendering for an immersive communication network. This
paper proposes a method for reverberation morphing by
relocating the poles and zeros of the transfer function. It
assumes that the distance of the pole/zero locations from
the unit circle in the z-plane represents the reverberation
condition for the transfer function. Exponential timewindowing
moves the minimum-phase zeros, while the
pole/zero relocation for the all-pass part is possible by the
windowing after causal and non-causal cepstrum decomposition.
We confirmed that the reverberation effects on
the frequency response rendered by the proposing method
were similar to those for recorded impulse responses in a
variable reverberation room. This morphing is also applied
to stable inverse filtering in a reverberant space.
INTRODUCTION
An immersive communication system requires rendering
of auditory events including 3-D spatial sound to enable
effective collaboration through an interactive sound field
network [1-3]. Rendering and morphing of room reverberation
are crucial technology of auditory events modeling
in virtual acoustics. This paper describes a 3D-sound
morphing by reverberation control using cepstrum decomposition.
Reverberators have been investigated as an effective
tool for sound recording and reproducing since many
years ago[4]. However reverberators that naturally sound
such as real-room reverberation are still under study. Tohyama
et al.[5] proposed a new method for generating an
impulse response which represents reverberation characteristics
based on superposition of free-oscillations whose
frequencies are determined based on the modal statisitics.
Modification of the Magnitude Response
The transfer function can be decomposed into the minimum-
phase and all-pass components. Figure 3 is a sample
of impulse response (Fig.3 (a)) with the decomposition
into the minimum-phase (3(b)) and all-pass (3©) components
in terms of poles and zeros. Relocating the poles
and zeros as illustrated in Figs 3(b) and 3©, the magnitude
and phase can be controlled.
MORPHING OF ROOM REVERBERATION
Let' s take the example shown in Fig.2. Figure 7 presents
the minimum-phase magnitude and all-pass phase responses
after the morphing by exponential timewindowing
with a negative exponent. We can confirm
similar effect to Figs. 4 and 6 on the minimum-phase and
all-pass components.
SUMMARY
We have described a method for reverberation morphing
based on relocating the poles and zeros of the transfer
function. Different from the modal theory, we assumed
that the distance of the pole/zero locations from the unit
circle in the z-plane represented the reverberation condition
for the transfer function. The proposed method can be
performed separately; by exponential time-windowing for
the minimum-phase part, and the same windowing for the
non-minimum components after causal and non-causal
cepstrum decomposition.