Electrical audio signal processing systems and devices – Sound effects
Patent
1996-05-14
1998-05-26
Loomis, Paul
Electrical audio signal processing systems and devices
Sound effects
381 17, 381 74, H03G 300
Patent
active
057579318
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a signal processing apparatus and an acoustic reproducing apparatus, and particularly to a signal processing apparatus using an FIR filter and an acoustic reproducing apparatus using such a signal processing apparatus.
BACKGROUND ART
Heretofore, there have been proposed many electronic devices wherein an impulse response of a system such as a signal transmission line is measured and such impulse response is reproduced by an FIR filter arranged in a signal processing apparatus. A reverberation apparatus using an FIR filter measures an impulse response of a room and the FIR filter reproduces such an impulse response so that a reproducing signal having the same reverberation characteristic as that obtained when sounds are reproduced in the room where the impulse response was measured can be reproduced under thoroughly different circumstances.
An acoustic reproducing apparatus using an FIR filter disposes an FIR filter for measuring an impulse response expressing a transfer characteristic of sounds emanating from speakers of a headphone to the listener's ears in a signal processing apparatus. Therefore, the above acoustic reproducing apparatus using the headphone can achieve a sound image localization effect equivalent to that obtained when sounds are reproduced by the speaker system.
However, in such a signal processing apparatus, when a filter having a converging time and frequency response faithful to the measured impulse response is composed of an FIR filter with high accuracy, it is necessary to use an FIR filter having a long tap length. Accordingly, many units of signal processing apparatus are required for such a signal processing, thereby an expensive and large-scaled system is required.
DISCLOSURE OF THE INVENTION
According to the present invention, an inputted digital audio signal is divided into signals of at least two frequency bands. The signal containing at least the low band frequency component of the divided signals is sampled by a sampling frequency lower than a sampling frequency of the inputted digital audio signal, and impulse responses ranging from a previously-measured sound generation source to a measuring point are superimposed upon the sampled signal by FIR filters. Therefore, the signal can be satisfactorily processed by use of even the FIR filter with the short tap length.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram of a signal processing apparatus according to a first embodiment of the present invention;
FIG. 2 is a block diagram of an FIR filter used in the embodiment;
FIG. 3 is a block diagram of a signal processing apparatus according to a second embodiment of the present invention;
FIG. 4 is a block diagram of a signal processing apparatus according to a third embodiment of the present invention;
FIG. 5 is a block diagram of a signal processing apparatus according to a fourth embodiment of the present invention;
FIG. 6 is a block diagram of a signal processing apparatus applied to an acoustic reproducing apparatus according to the embodiment of the present invention;
FIG. 7 is a block diagram of a signal processing apparatus applied to an acoustic reproducing apparatus according to the embodiment of the present invention;
FIG. 8 is a block diagram of a signal processing apparatus according to a fifth embodiment of the present invention;
FIG. 9 is a block diagram of an FIR filter used in the fifth embodiment;
FIG. 10 is a graph showing an example of a measured impulse response;
FIG. 11 is a graph showing a signal delayed by a time t1 by a delay circuit and which is further attenuated;
FIG. 12 is a block diagram of a signal processing apparatus according to a sixth embodiment of the present invention;
FIG. 13 is a block diagram of a signal processing apparatus according to a seventh embodiment of the present invention;
FIG. 14 is a block diagram of an FIR filter;
FIG. 15 is a block diagram of a signal processing apparatus according to an eighth embodiment of the present invention;
FIG. 16 is a block diagram of
REFERENCES:
patent: 4338581 (1982-07-01), Morgan
patent: 5025472 (1991-06-01), Shimizu et al.
patent: 5173944 (1992-12-01), Begault
Inanaga Kiyofumi
Yamada Yuji
Lee Ping W.
Loomis Paul
Maioli Jay H.
Sony Corporation
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