Electrical audio signal processing systems and devices – Including amplitude or volume control
Reexamination Certificate
1999-06-01
2001-02-27
Harvey, Minsun Oh (Department: 2747)
Electrical audio signal processing systems and devices
Including amplitude or volume control
C381S098000, C381S119000, C381S123000
Reexamination Certificate
active
06195439
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an audio signal processing apparatus and is suitably applicable to an audio input signal processing apparatus, such as an audio mixer, which controls the frequency characteristics and amplitudes of audio input signals when the audio input signals are mixed, for example.
BACKGROUND ART
Conventionally, an audio mixer used for processing audio signals is equipped with a frequency processing section and an amplitude processing section. The frequency processing section includes, for example, filters which controls the frequency characteristics of the inputted audio signal. The amplitude processing section is generally referred to as a fader or a dynamics which changes the amplitudes of the inputted audio signal. Using these sections, a signal processing usually called an effect processing is performed for the frequency characteristics and amplitudes of the inputted audio signal.
When performing the effect processing to change the frequency characteristics, two frequency processing operations such as rejection of signal components by a filter and emphasis of signal components by an equalizer can be carried out in any order and the resulting frequency characteristics are the same.
If the audio signal inputted to the audio mixer has a signal level below the predetermined threshold, then performing the amplitude processing on the audio signal using, for example, a compressor will not cause any changes in the amplitude of the audio signal. In contrast, if an equalizer is placed at the former stage of the compressor so as to increase the amplitude level of the signal in a predetermined frequency range to a level above the threshold and then an amplitude processing is performed, the amplitude of the output signal varies in accordance with that of the input signal. In other words, the characteristics of the output signals are different whether the equalizer performs the amplitude processing before the amplitude processing of the compressor or not. Therefore, when processing signals using the audio mixer, the amplitude processing is usually performed on input signal at a fixed stage taking into consideration the influence of the amplitude processing.
In order to perform the amplitude processing on output signals having a variety of frequency characteristics and amplitude characteristics, it has been proposed to perform the effect processing by adding a switcher which allows switching of the dynamics to desired stages of the frequency processing and/or amplitude processing.
Referring to
FIG. 3
, in a mixer
1
, an input trim
3
performs fine adjustment on an audio input signal S
1
which is inputted from an input terminal
2
thereto, and outputs the adjusted signal to a frequency processing section
1
A so as to perform the frequency processing for each frequency range.
The audio input signal S
1
, which is inputted via the input terminal
2
, is sent out through a main signal line BL to a signal characteristic processing section which includes an amplitude processing section, such as a fader
7
, and the frequency processing section
1
A. When the signal passes through the frequency processing section
1
A, a high-pass filter (HPF)
4
rejects a DC component of the signal and low frequency noise components such as the sounds of wind, and a low-pass filter (LPF)
5
rejects high frequency noise components. Further, an equalizer (EQ)
6
emphasizes or rejects, for example, the voices (vocal) of human beings and particular sounds of music instruments such as cymbals. After the frequency processing performed by the respective stages of the frequency processing section
1
A, the fader
7
adjust the output level of the audio signal and an output terminal
8
outputs the adjusted audio signal.
The mixer
1
includes selector switches SW
1
to SW
7
which connect and disconnect between the input terminal
2
, input trim
3
, high-pass filter
4
, low-pass filter
5
, equalizer
6
, fader
7
, and output terminal
8
. The selector switches SW
1
to SW
7
have their respective contacts connected to a dynamics
10
via matrix switchers
9
A and
9
B. The matrix switchers
9
A and
9
B are switched so as to place the dynamics
10
between any adjacent two of input terminal
2
, input trim
3
, high-pass filter
4
, low-pass filter
5
, equalizer
6
, fader
7
, and output terminal
8
.
FIG.
4
(A) illustrates the selector switches SW (SW
1
to SW
7
) which selectively switch the main signal line BL that connects the input terminal
2
, input trim
3
, fader
7
, output terminal, and the respective frequency processing sections, each of the selector switches having four contacts
11
A,
11
B,
12
A, and
12
B. For example, when the dynamics
10
is selected, the contacts
11
A is connected to the contact
12
A and the contact
11
B is connected to the contact
12
B as shown in FIG.
4
(B). At the other stages where the dynamics
10
is not inserted, the contacts
11
A are connected to the contacts
11
B and the contacts
12
A are not connected to the contacts
12
B as shown in FIG.
4
(C).
The dynamics
10
includes signal amplitude processing means such as a limiter and compressor that decreases an high output level, and an expander and a gate that cuts cross talk appearing in the low output level. Thus, using the matrix switchers
9
A and
9
B, the mixer
1
performs the amplitude processing on the inputted audio input signal S
1
based on an output signal from any one of the input terminal
2
, input trim
3
, high-pass filter
4
, low-pass filter
5
, equalizer
6
, fader
7
, and output terminal
8
, in order to output an output signal, that is, the mixer
1
sets the output level.
Since the mixer
1
having the aforementioned configuration inserts the dynamics
10
into a desired stage of the main signal line BL by switching the selector switches SW
1
to SW
6
, the apparatus suffers from a problem that the audio input signal S
1
is disconnected during a moment when the selector switches are switched and switching noise generated by the switchers is mixed with the audio signal which is being transmitted over the main signal line BL.
Also, the buses in matrix form in the matrix switchers
9
A and
9
B are complex in construction and costly accordingly. In order to prevent the audio input signal S
1
from being disappearing during the switching operation, the matrix switchers
9
A and
9
B provided in the mixer
1
should be switched by a selection signal having a time constant. This makes the construction of the switcher more complex.
DISCLOSURE OF THE INVENTION
The present invention was made in view of the aforementioned drawbacks. The present invention provides an audio signal processing apparatus where switching noise is prevented from entering into the transmitted signal when switching to selectively derive an output from a desired stage of the signal characteristic processing section which performs the frequency processing and/or the amplitude processing on the signal when setting output level of the output signal.
In order to solve the aforementioned drawbacks, an apparatus according to the present invention has one or a plurality of signal characteristic processing means which receives an audio input signal and changes the frequency characteristic and amplitude characteristic of the audio signal; a plurality of signal lines which receive a signal output from an input stage of a signal characteristic processing means into which the audio signal enters, and from the output stage of one or a plurality of signal characteristic processing means; a level control signal generating means which generates a control signal for determining an output level on the basis of the signal output received over the signal lines selected, the output level being determined in accordance with the output of a selecting means which selects one of a plurality of signal lines; and an output level setting means which adjusts the output level on the basis of an output signal derived from a selected signal characteristic processing means, and outputs as an audio outpu
Harvey Minsun Oh
Maioli Jay H.
Sony Corporation
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