Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The present invention relates to apparatus for pro-
ducing a plurality of audio sound effects and more specifically
for producing sound effects for electronic games such as shots,
explosions, motors, gongs and ~et plane and automobile sounds.
Present techniques used in electronic games for pro-
ducing sound effects include analog noise sources whose output
is shaped by a voltage controlled amplifier to provide a proper
decay or envelope characteristic. Alternatively, digital
polynomial counters are also used as the analog noise source.
One disadvantage of the foregoing is that the analog
portions of the circuit are not suitable for large scale inte-
gration. This is an especially critical cost consideration when
home or consumer type video games are to be connected to a home
television receiver. Secondly, the present sound effect
techniques are usually special purpose directed to one or two
sound effects at the most. Individual sound effect generators
are used for each effect, resulting in a large number of separ-
ate circuits for each game.
OBJECTS AND SUMMARY OF THE INVENTION
It is, therefore, a general object of the present
invention to provide improved apparatus for producing audio sound
effects.
It is another object of the invention to provide
apparatus as above which produces a plurality of audio sound
effects the apparatus being suitable for large scale integration.
In accordance with the above objects there is provided
an apparatus for selectively producing any one of a plurality of
predetermined sound effects each specified by an associated
digital command character, said apparatus comprising: variable
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clock means for generating a binary clock signal have a frequency
specified by an associated digital command character, said clock
means including an input terminal adapted to be coupled to a
source of timing signals, an output terminal for manifesting said
binary clock signal, a data input terminal adapted to be coupled
to said associated digital command character, and means coupled
to said input terminal, said output terminal and said data input
terminal for transforming said timing signals to said binary
clock signals; and sound generator means for generating sound
effect signals corresponding to said associated digital command
character, said sound generator means including an input terminal
coupled to said output terminal of said variable clock means, an
output terminal for manifesting the electrical analog signals
corresponding to said desired sound effect, counter means
coupled to said input terminal and said output terminal for gener-
ating a binary signal train in response to the receipt of said
binary clock signal, said binary signal train having a frequency .
content specified by said digital command character, and means
: coupled to said counter means for converting said binary signal
train to said electrical analog signals corresponding to said
desired sound effect, said converting means including means for
providing a predetermined amplitude attenuation characteristic
corresponding to said desired sound effect specified by said
digital command character.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram embodying the present
invention;
Figures 2A through 2E are various waveforms showing
some of the sound effects produced by the present invention;
Figure 3 is a block diagram of one embodiment of the
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present invention;
Figure 3A is an associated timing diagram useful in
understanding Figure 3; and
Figures 4A-D are circuit schematics of another embodi-
ment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figure 1, a variable clock 10 drives
a variable digital noise generator 11 which may, for example,
be a polynomial counter. The noise generator may be varied to
provide either white noise, regular waveforms for tones, or
irregular waveforms for motor sounds. The variable clock contains
the pitch of generated tones. For example, if white noise is
selected, the variable clock can change the pitch from a pistol
shot to an explosion. The output of noise generator 11 has its
decay characteristic (that is, its envelope) controlled by
amplitude control unit 12 which provides an audio output.
Figures 2A through E show different types of sound
effects and specifically Figures 2B, 2C and 2D illustrate the
different sound effects obtained by varying the decay of the
envelope and the waveform generated. For example, a shot has
approximately a 1/4 second decay time, an explosion to two
seconds and a gong one to two seconds. The type of noise gener-
ated by noise generator 11 also is an important criterion where
the shot and explosion utilize a white type of noise and the
gong a square wave. In addition, the variable clock 10 provides
for the shot, a noise frequency of approximately 1,500 Hz and
for the explosion a lower pitched noise frequency of 150 Hz.
Figure 2A shows the waveform of a motor such as an idling motor
which may range in frequency from 10 to 100 Hz and Figure 2E a
jet plane sound where the envelope is constant and the pitch
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varies. This is produced by a variation of clock 10. For a
single sound effect it may be necessary to vary the clock fre-
quency to ten different settings. This would be to simulate a
steady acceleration. In simulating a race car, 16 different
frequencies might be used.
In any case, the illustrations of Figure 2 are merely
representative of the many sound effects created by the present
invention and, of course, the frequencies and timings given are
only typical examples.
Finally, although the generator 11 is termed a "noise"
generator, it is still capable of producing relatively sinus-
oidal or tonal sounds.
One embodiment of the invention is shown in Figure 3
which utilizes a 24 stage polynomial counter 13 as a noise gener- -
ator and is driven by a variable clock source. The counter has
a feedback loop including the gate 14. The last five stages 20
through 24 are illustrated which are connected to AND gates 16a
through d. The outputs of these AND gates are connected to an
OR gate 17 and through a low pass filter 18 provide an audio
output. Amplitude or decay of the audio output is controlled
in essence by reducing the density or duty cycle of the gated
output. As indicated by the associated timing diagram in
Figure 3A the output 21 of the polynomial counter 13 is delayed
a longer time than output 20. And if these two outputs are
combined by turning gate 16a on, a lower duty cycle or lower
density will result producing in effect a lesser perceived ampli-
tude and a softer volume. AND gates 16a-d are controlled by an
amplitude control unit 19 which in turn is controlled by a pre-
programmed microprocessor.
Thus, in summary, the circuit of Figure 3 provides
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for selective summing of a plurality of stages of a polynomial
counter to ef~ectively vary the perceived amplitude of the audio
output wave and thus control its decay or envelope characteristic
and the resulting sound effect. Amplitude control unit 19
includes digital control inputs which are thus easily controllable
by an associated micro-processor.
Another embodiment of the invention is shown in Figures
4A-D where in Figure 4A the variable clock 10 is shown in detail.
This includes a divide by N counter 21 driven by a 30 kHz clock
input whose division is controlled by a four bit data register
22. The data register has digital inputs D0 through D4 which
determine the final frequency output on line 23 of variable
clock 10. A decode table is listed in Figure 4A and includes the
possibility of division by two up to division by 32. The indi-
cated data bus to the data register 22 is from, referring to
Figure 4B, the microprocessor 24 which has a data bus 26 and an
address decode control line 27. This control line provides for
a time share type of loading and control of register 22 and two
other data registers illustrated in Figures 4B and 4C.
Still referring to Figure 4B, the four bit data register
28 receives bits D0 through D3 from the data bus 26 to provide
- a variable digital noise generator. The generator includes a
five bit polynomial counter 29 and a four bit polynomial counter
31 which are linked together by the illustrated gating. Counter
29 may function as a prescaler. Five bit counter 29 has five
D-type flip-flops and counter 31 four D-type flip-flops. Var-
iable clock output on line 23 is directly coupled to the clock
inputs of the five clock (C) inputs of the five bit polynomial
counter 29 and inverted through NOR gate 32 and then coupled to
the clock inputs of four bit counter 31.
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Thus, the noise generator of the embodiment of
Figure ~B can provide a nine stage polynomial counter, or other
configurations depending on the programmed feedback paths, which
is believed to provide the maximum flexibility for producing
different types of sound effects at a minimum cost. An eight
stage counter will not produce as adequate a range of noise type
sound effects nor would the quality of each sound effect be as
effective. The longer the polynomial counter is, of course, the
greater the number of shift sequences before any repitition occurs
and therefore theoretically a puretype of white noise may be pro-
duced. On the other hand, the gating as illustrated also pro-
vides for division of the effective square wave on line 23 to
provide a relatively pure pitched or tonal audio sound.
The associated Table I indicates the different varia-
tions of the noise generator 4B with full hexadecimal range 0
through 9 and A through F by the variation of the four binary
control inputs D0 through D3. In the hexcode zero all stages
are set to 1 which is used for testing or providing sound effects
by the amplitude control stage of Figure 4C. The remaining
combinations provide a very pure division of the clock frequency,
a polynomial noise counter effect or a combination of the two.
For example, hexcode eight combines all nine stages together to
provide a "white" noise.
In operation with hexcodes 1 through 3 the four bit
polynomial noise counter 31 is in operation with a feedback on
line 33. This line is connected to a gate 34 which has an out-
put when the D2 and D3 inputs are zero. Note this is the con-
dition of hexcodes 1, 2 and 3.
Next, if D2 and D3 are both one as shown in hexcodes C
through F, four bit polynomial counter 31 acts as a three bit
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twisted ring having a one output on feedback line 36, and drives
the gate 37 which has as its other two inputs the inverted D2 and
D3 which are both zeroes to make the gate effective. Gate 38
provides typical OR action. Gate 39 corresponds to the hexcode
zero where all binary inputs are zero.
Referring to Figure 2 and the representative sounds,
the motor might be provided by the hexcode 3 since the five bit
polynomial counter prescaler driving a four bit polynomial
counter produces a pl~usible motor sound. A shot or e~plosion
utilizes white noise; thus it is provided by hexcode eight.
A gong may use a square wave and thus no polynomial noise gener-
ation counting action butrather just division, for example, is
provided by hexcodes four and five. Lastly, a jet plane would
again be provided by the white noise of hexcode eight.
The output 41 of the noise generator of Figure 4B is
shaped by the amplitude control unit 12 illustrated in Figure 4C.
Here a four bit data register 42 controlled by bits D0 through
D3 from the data bus 26 provide for digital control at any
instant in time of the amplitude of the audio output; in other
words, the decay envelope. Data register 42 drives what is an
effective digital to analog converter 43 which utilizes the gated
resistive summing of the type shown in Figure 4D where the
weighted resistors R, 2R, 4R and 8R are selectively used to con-
trol amplitude providing an analog output in response to a digi-
tal input. However, the weighted resistors may be actually MOS
type transistors 44a-d driven by the representative NOR gates
46a-d (which are actually AND type functioning gates). MOS
transistors 44 provide the different resistances by varying the
the drain or source area with the drain area, for example, of
transistor 44d being 16 times as large as 44a.
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The deeoding scheme is also shown in Figure 4C with
a 0001 binary input producing the lowest audio output pull down
eurrent meaning the smallest amplitude and 1111 the highest
amplitude. The mieroproeessor (Figure 4B) provides on an on-
line basis the instantaneous proper eontrol eode to produee the
envelopes as shown in Figures 2A through E. A typical miero-
proeessor can easily provide a new control instruction every 1/60
seeond. Thus, several eontrol instructions can be provided, for
example, in 1/4 second to provide a very effeetive shot envelope
of Figure 2B. The amplitude control unit of Figure 4C is inten-
ded to be implemented in large scale integration especially by
the technique of the different areas for the resistive summing
of the digital to analog converter 43. Also noise generator 11
in both of its forms is also easily integrated since it produces
a digital output.
As illustrated in Figure 4C, the amplitude control unit
is connected to single output line 41 of the noise generator.
Each gate 46A-d eould be eonneeted to different points of the
polynomial eounter to achieve a somewhat different sound effect.
Thus, in summary the present invention provides an `
improved apparatus for producing a plurality of different audio
sound effeets whieh are variable by the digital eoding from a
mieroprocessor. All the apparatus is easily implemented in
large seale integration.
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TABLE I
HEXCODE D3 D2 DlD0 TYPE OF NOISE OR DIVISION
0 0 0 0 0 SET TO 1
1 0 0 0 1 4 BIT POLY
2 0 0 1 0 15~ 4 BIT POLY
3 0 0 1 1 5 BIT POLY 4 BIT POLY
(MOTOR SOUND)
4 0 1 0 0 ,2 (TONES)
0 1 0 1 .2
6 0 1 1 0 .31
7 0 1 1 1 5 BIT POLY ~ .2
8 1 0 0 0 9 BIT POLY (WHITE NOISE)
9 1 0 0 1 5 BIT POLY
A 1 0 1 0 .31
B 1 0 1 1 SET LAST 4 BITS TO 1
C 1 1 0 0 '.6
D 1 1 0 1 .6
E 1 1 1 0 .93
F 1 1 1 1 5 BIT POLY .6
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