JP3256045B2 - Audio output circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio output circuit suitable for use in audio equipment and video equipment for performing stereo reproduction.

[0002]

2. Description of the Related Art Conventionally, as audio equipment for performing stereo reproduction, there are a system component, a CD radio cassette player (a tape recorder with a radio incorporating a compact disc player), and the like, for example, left and right channel speakers, an amplifier, a tape deck, and the like. In the system components separated from each other, the left and right speakers are arranged to be separated from each other in front of the listener to the left and right to perform stereo reproduction.

However, when actually used by the user, the left and right speakers of the system components and the like are arranged adjacent to both sides of the stereo body incorporating an amplifier, a tape deck, etc., and are arranged in the same manner as a speaker-type CD radio cassette player. Used in Therefore, since the distance between the left and right speakers is not sufficient for stereo reproduction, the sense of sound spread is impaired and a sufficient stereo effect cannot be obtained.Conventionally, left and right channel audio signals are extracted as additional signals of each other. The phase of the signal whose level and phase are controlled is inverted, and the left channel component is added to the right channel, and the right channel component is added to the left channel, thereby obtaining a sound spread.

More specifically, as shown in FIG. 13, left and right channel audio signals which are converted into digital signals by an A / D converter and input to left and right channel input terminals 4L and 4R are respectively extracted as additional signals. Left and right channel attenuators 2L, 2L,
R, the left and right channel system phase control circuits 3L and 3R for controlling the phases of the signals whose levels are controlled by the two attenuators 2L and 2R, respectively, the level attenuation amounts of the two attenuators 2L and 2R, and the two phase control circuits 3L and 3L. A control circuit 10 (for example, a microcomputer, hereinafter referred to as a microcomputer) for controlling the phase shift amount in the 3R based on the listening position information for the left and right channel speakers 9L and 9R, respectively;
A left channel delay circuit 4L for delaying the digitally converted left channel audio signal from the left channel input terminal 1L, and a digitally converted right channel audio signal from the right channel input terminal 1R. A right-channel delay circuit 4R, a left-channel adder 5L for inverting the phase of the signal whose phase has been controlled by the right-channel phase control circuit 3R and adding the delayed left-channel audio signal, and this delay; A right-channel adder 5R for inverting the phase of the signal whose phase has been controlled by the left-channel phase control circuit 3L and adding the added signal to the right-channel audio signal thus obtained; And left and right channel D / A converters 6L and 6R for converting the left and right channel audio signals to the original analog signals. .

The conventional circuit further includes a distance measuring circuit 11 for measuring the distance from the audio equipment to the listener P. For example, the distance sent by the listener P operating a remote control transmitter is provided. The distance to the listener P is measured by receiving the information signal, and the distance is input to the microcomputer 10. Note that the distance between the left and right channel speakers 9L and 9R can be manually input by the listener. In this case, the left and right channel speakers 9L and 9R are arranged adjacent to both sides of the stereo main body, and one speaker is provided. It is known because it has an arrangement similar to that of a physical CD boombox.
Etc. are stored.

For this reason, the microcomputer 10 uses the distance from such an acoustic device to the listener P and the distance between the left and right channel speakers 9L and 9R as listening position information.
At each listening position, the level and phase of the additional signal for obtaining the optimum stereo effect are calculated, and both attenuators 2
L, 2R and the two-phase control circuits 3L, 3R
And the amount of phase shift in the control.

For example, as shown in FIG. 14, when the listener P is listening at a distance L3 from the audio equipment, the spread angle θ of the left and right channel speakers 9L and 9R.
Since 3 is 30 ° or more, it is assumed that a sufficient stereo effect can be obtained only with the vector F1 of the right channel audio signal, and the magnitude of the vector F2 of the additional signal is set to zero. When the distance from the audio device becomes L4 and the vector angle of the right channel audio signal (the spread angle θ of the right channel speaker 1R) becomes 30 ° or less, the vector F7 of the right channel audio signal and its addition are added. The combined vector F9 with the signal vector F8 has the same magnitude as the right channel audio signal vector F7 at an angle of 30 °.
The level and phase of the vector F8 of the additional signal, that is, the angle and the magnitude are set. Similarly, even if the distance of the listener P becomes L2, the composite vector F6 of the vector F4 of the right channel audio signal and the vector F5 of the additional signal has an angle of 30.
The angle and the magnitude of the vector F5 of the additional signal are set so that the angle becomes equal to the magnitude of the vector F4 of the right channel audio signal in degrees. In this way, the listener P always hears the left and right channel speakers 1L, 1L,
It will feel as if there is R, and a stereo effect will be obtained.

More specifically, assuming that the distance to the listener P is L and the distance between the left and right channel speakers 9L and 9R is W, the left and right channel speakers 1L and 1R move forward and to the left and right as viewed from the listener P. The divergence angle θ is determined by θ = tan ^-1 {L / (W / 2)}, from which the phase and level of the additional signal, that is, the angle and magnitude of the additional signal vector from the opposite phase can be calculated. For example, as shown in FIG. 15, the vector Fm of the right channel audio signal from the right channel speaker 9R and the inverted right channel audio signal from the left channel speaker 9L, that is, the additional signal vector Fs, are used as the right channel audio signal Fs. Considering the case of only an audio signal, the angle Φ and the magnitude | Fs | are as follows: Φ = 180 ° −90 ° −2θ− (30 ° −θ) / 2 = 75 ° −3θ / 2 | Fs | = | Fm | × 2 × sin {(30 ° −θ) / 2} (however, θ ≦ 30 °).

[0009] In this way, the combined vector of the right channel audio signal vector and the additional signal vector is the same as the right channel audio signal vector, regardless of where the listener P listens before and after. The size is such that the sound can be heard from the direction of the spread angle of 30 °. For example, as shown in FIG. 16, the vector angle of the right channel audio signal is 30 ° (the spread angle θ of the right channel speaker).
, The additional signal vector F11 is Φ = 30 °, |
F11 | = 0, the resultant vector F12 has the same angle and the same magnitude as the vector F10 of the right channel audio signal. When the vector angle of the right channel audio signal is 0 ° as shown in FIG. 17, the additional signal vector F14 is Φ = 75 °, | F14 | = | F13 | × 0.
52, the synthesized vector F15 has the same size as the vector F13 of the right channel audio signal, and has an angle at which sound can be heard from the direction of the spread angle of 30 °.
The same applies to the case of a left channel audio signal.

FIG. 18 shows a flowchart of such a control operation of the microcomputer 10. First, the microcomputer 10 starts its control operation based on a control program stored in a program ROM or the like. In this case, the distance W between the system speakers 9L and 9R is read from the data ROM, and the distance L to the listener P is read from the distance measurement circuit 13 in the next step # 10. And
In the next step # 15, it is determined whether or not the distances W and L read are the same as the values used in the previous control, and if they are the same, the previous control state may be left, and the control operation is ended. Will be. If not the same, step # 20
To determine the spread angle θ of the left and right channel speakers.

Then, in step # 25, it is determined whether or not θ is 30 ° or more. If it is determined that θ is larger, the process proceeds to step # 30, and the angle Φ of the additional signal vector is obtained. Then, the process proceeds to step # 35 to determine the magnitude | Fs |, and in the next step # 40, the level attenuation in the left and right channel attenuators 7L and 7R and the phase in the left and right channel system phase control circuits 8L and 8R. After performing the control with the shift amount, the control operation ends. If it is determined in step # 25 that θ is 30 ° or more, the flow proceeds to step # 45, where the magnitude of the additional signal vector | Fs |
Then, the process proceeds to step # 40.

[0012]

However, such a conventional audio output circuit has an effect on the vertical line of the left and right channel speakers, that is, in the front and rear direction between the speaker and the listener, but the left and right sides of the listener are not effective. In the direction, the sound spreading effect was small.

For this reason, the listener moves the speaker itself or the main body of a CD radio cassette player or the like so that the left and right speakers face the front of the listener. Further, in the conventional circuit, there is no problem with left and right independent sounds, but there is a disadvantage that the signal level is attenuated and the sound quality is changed for a signal present on both the left and right, that is, a sound whose sound is near the center.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and takes out a left-channel audio signal as an additional signal, controls the level and reverses the phase, and converts the left-channel audio signal into a right-channel signal. Left and right channel audio to which the additional signal has been added in an audio output circuit for extracting the right channel audio signal as an additional signal to the system audio signal and controlling the level, inverting the phase, and adding the inverted signal to the left channel signal. A delay circuit that receives each signal, and an ultra
The left and right channels receiving an ultrasonic wave out of a sound wave and an infrared pulse
Super sound attached to the speaker or speaker part of the channel
Wave receiving element and infrared light receiving section for receiving the infrared pulse
And after receiving the infrared pulse,
Measure the time until receiving the ultrasonic wave, the measured
Based on the difference data of the left and right time,
A control means for setting a delay time and controlling the delay circuit is provided.
It is a digit.

Further , the present invention is based on the measured time.
Audio output circuit to adjust the left and right channel gain
To provide.

The present invention also relates to left and right channel speakers.
While receiving ultrasonic waves while its speaker band
The characteristics of the pass filter and the ultrasonic frequency
Eve output amplifier frequency and speaker impedance
Audio output circuit to set based on the
You.

Further, according to the present invention, a left-channel audio signal is extracted as an additional signal, and the right-channel audio signal is attenuated by passing it through an attenuator before the level and phase are controlled. An additional means for adding to the left channel additional signal, and a means for controlling the level and phase of the signal output from the additional means, inverting the phase and adding it to the left channel signal,
On the other hand, the right channel audio signal is extracted as an additional signal, and before the level and phase are controlled, the left channel audio signal is attenuated through an attenuator, and the inverted signal is added to the right channel additional signal. An audio output circuit provided with an adding means, for controlling a level and a phase of a signal output from the adding means, and for providing a means for inverting the phase and adding the inverted signal to a right channel signal, thereby controlling the spread of left and right sounds; Is provided.

[0018]

As described above, by using the means of the present invention,
Regardless of whether the listening position is to the left or right of the left and right speakers of the stereo device, the stereo enlargement effect obtained in front can be obtained, and the stereo enlargement effect can be automatically obtained in the listener direction by using the ultrasonic remote control. can get.
Furthermore, by using together with the infrared remote controller, the distance between the speaker and the listener can be measured, so that not only the right and left direction of the listener but also the stereo effect can be controlled optimally by enlarging or reducing the stereo effect. No matter how far apart the speakers are, the distance to the listener can be known, so that the delay time can be easily calculated and the optimum stereo effect can be obtained.

Further, by attenuating the left and right audio signals into the additional signals of the left and right audio signals and adding the inverted signals to the additional signals of the respective opposite channels, the stereo central audio signal is hardly attenuated. As a result, the stereo effect can be expanded without causing a change in sound quality.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an audio output circuit according to the present invention. FIG. 1 is a block-like electric circuit showing an embodiment of an audio output circuit according to the present invention, and the same parts as those of the conventional circuit are denoted by the same reference numerals for convenience of explanation.

Before describing the circuit, a sound image at a listener position to be solved in the present invention will be described with reference to FIGS. When the listener listens to the position of P1 in FIG. 2, that is, the listener listens to the front of the left and right speakers, the left and right speakers 9L and 9R spread out to the positions 9L 'and 9R' as described in the description of the conventional circuit. The inverted signal vector at this time is F2, and a composite vector F3 with the basic signal F1 is obtained.
It becomes a sound image that spreads. However, at the position P2, the inverted signal vector becomes a vector F5 that is close to the same phase as the basic signal F4. This is due to the fact that the loudspeaker of 9L is farther than 9R, which causes a time delay and the movement of the vector. The time delay is due to the distance between the left and right speakers, and the sound velocity at room temperature is about 344 m /
S: If the difference between the distance between the listening position P2 and the 9R speaker from the listening position P2 and the distance between the listening position P2 and the 9L speaker is 34.4 cm, the delay is 1 msec.

Now, considering the phase at the position P3, FIG.
, A phase delay occurs in a portion C between the position P3 and the speaker 9L. This problem can be corrected by advancing the phase of the audio signal of the speaker 9L. However, in digital signal processing, the signal of the speaker 9R can be converted to the signal of the speaker 9L without any change because the signal of the speaker 9L can be easily delayed. This is possible by delaying the phase (time) delay. This allows the left and right speakers to be viewed at the same distance even at the P3 position. That is, the sound image 9R'9L 'is obtained in the same manner as in the state where the sound image 9R is lowered backward from the position P1 in FIG. However, in this case, the speaker 9
Since the level of the speaker 9R is higher than that of the speaker 9L, the pseudo position (sound image) of R is the position of 9R 'in FIG.

The circuit of the present invention shown in FIG. 1 shows an audio output circuit for obtaining such a sound image, and has basically the same circuit elements as the conventional circuit, but is particularly characterized. The power configuration is different from the conventional circuit in that the left and right channel system adders 5L and 5R and the left and right channel system delay circuits 4L,
The point where the position of 4R is replaced, and each delay circuit 4L,
4R is characterized in that each of the 4Rs is configured to execute a delay operation in accordance with an operation of the key 12 via the microcomputer 10. In short, the listener can freely adjust the delay amount of the delay circuits 4L and 4R using a remote controller or the like.

FIGS. 4 and 6 show an embodiment in which the ultrasonic waves are used to control the delay time of the left and right channel signals L and R. FIG. 4 shows the ultrasonic receiving elements 22L and 22R.
In FIG. 6 , the bandpass filters 13L and 13R are provided in the speaker circuit so that only the ultrasonic waves can be detected since the left and right speakers are used as the receiving units. The outputs of these ultrasonic receiving elements and filters are output from the preamplifier 1
Amplified by 4L, 14R and re-bandpass filter 1
Only the ultrasonic waves are extracted at 5L and 15R, converted into logic level pulses by the next Schmitt triggers 16L and 16R, and input to the microcomputer 10.

The band pass filter 1 of the speaker section
FIG. 5 shows the characteristics of 3L and 13R. Since the frequency of the output amplifier is 20 Hz to 20 kHz, the impedance must be negligible with respect to the speaker impedance of 4 Ω to 8 Ω, and the ultrasonic frequency is 40 kHz.
By setting the frequency to about kHz and the impedance to a value sufficiently larger than the impedance of the speaker, the attenuation of the ultrasonic signal appearing at both ends of the speaker when receiving the ultrasonic wave can be reduced. When using an ultrasonic receiving element
As shown in FIG. 4 , the circuit configuration is independent of the speaker. By locating the elements 22L and 22R above the center of the speaker, subsequent calculations of distance, delay time, and the like can be handled in exactly the same way as when the speaker is used as a receiver.

Assume that the position of the listener is P3 shown in FIG. When the ultrasonic pulse signal is transmitted by the remote controller, the ultrasonic signal reaches the left and right speakers, and the bandpass filters 13L and 13R, the amplifier 14
L, 14R, band-pass filters 15L, 15R and Schmitt triggers 16L, 16R.
At this time, the time when the ultrasonic signal is first received by the speaker 9R is set as the start time, and the time (Td) until the ultrasonic signal is next received by the speaker 9L is measured.

Since the microcomputer 10 can delay the time difference (Td) for each sampling cycle in digital signal processing, if the sampling frequency is Fs, the microcomputer 10 sets the delay circuit 4R to Td × Td. Delay by Fs sample steps. The delay circuit 4L sets the delay to zero. FIG. 10 is a flowchart showing a series of operations of the microcomputer.

[0028] In FIG. 3, the delay in the control, the sound image position of the speaker 9R is becomes 9R ', right speaker absolutely sound of the right channel feel close closer. As shown in FIG. 6, B attenuators 17L and 17R are inserted between the adder and the delay circuit in the circuit of FIG. 4, and the attenuator 17L is set to 1 as shown in FIG. This is possible by reducing the attenuator 17R without attenuating.

In order to determine the amount of the decrease, an infrared remote control signal transmitted from an infrared remote control transmitter (not shown) is received by the infrared light receiving section 18 and, based on this signal, an ultrasonic input signal pulse (SR) of the right channel. The microcomputer 10 measures the time until the ultrasonic input signal pulse (SL) of the left channel. This is illustrated in FIG. 8, where the ultrasonic pulse SR is set to t1 seconds and the ultrasonic pulse SL is set to t2 seconds based on the infrared pulse signal α.
Since the speed of infrared light is higher than the speed of sound, it is possible to determine that an ultrasonic wave has been emitted at the time when the infrared light is input. If the sound speed of 344 m / sec is multiplied by the time of the ultrasonic wave, the distance from the speaker to the position P3 can be obtained. Is determined. or,
The sound pressure level is inversely proportional to the square of the distance.
The sound pressure ratio (PC) from the left and right speakers at the point is

(Equation 1) Since the upper right channel sound pressure is strong, the circuit needs to attenuate the attenuator 13R.

Since the power ratio applied to the left and right speakers is the sound pressure ratio of the left and right speakers, the power ratio Wc may be the reciprocal of the sound pressure ratio.

(Equation 2) If (1) and (2) are equal, then the left and right speaker sound pressure levels at point P3 are the same,

(Equation 3) Therefore,

(Equation 4) That is, the attenuator 17L is set to 1 and the attenuator 17
If R is t1 / t2, the pseudo right speaker 9R 'in FIG.
Moves in a pseudo manner at the same distance 9R ″ as 9L ′.

A description will be given of the right-channel speaker position correction in the case where an infrared pulse and an ultrasonic wave as shown in FIG. 6 are used. If the left channel signal is V _L and the right channel signal is V _R , an additional signal is added and the attenuator 1
7L, V _L signal at the output of the 17R ', V _{R' When, V L '= (V L} -AV R ∠φ) × B L ───── (a1) V R' = (V R - _{AV L ∠φ) × B R ─────} (a2) where, AV _L is the output of a attenuator 2L, AV _R is the output of the a attenuator 2R. At the listener position in FIG. 3, B _L = 1 and B _R = t1 / t2.
Substituting in 1, a2, a _{V L '= V L -AV R} ∠φ V R' = (V R -AV L ∠φ) × t1 / t2. For the right channel, the composite signal at the listener's position P3 is: Multiplying V _R coefficient vector F6 when not applied _{V R · t1 / t2 + AV} R ∠φ ───── (a3) coefficient of the attenuator t1 / t2, F6 '= V R · t1 / t2
Becomes In the equation (a3), the vector of AV _R ∠φ is F7, and the vector F6 has a small spread of 9R ′.
At 6 ', the width is 9R ", and the spread can be equal to the volume balance with the left channel, that is, the distance can be equalized.

Next, in the delay circuits 4L and 4R, the distance between the listener and the left and right speakers, that is, the arrival time difference of the sound wave is partially delayed by the left channel c, so that the phase angle of c is φc. AV _R ∠φ in equation (a3) becomes AV _R ∠ (φ-φc) ───── (a4), and the vector F7 is close to F6, and does not spread even if the vectors are combined. To restore this, the phase of the right channel is delayed by φc to relatively obtain the equation (a4).
Φc disappears, and F7 can be realized.

As for the delay time, the difference between the ultrasonic pulse time t1 and the ultrasonic pulse time t2 is calculated, the delay of the delayed channel is made zero, and the delay of the earlier channel is | t1-t2 | Delay time. Also in this case, similarly to the above, the digital processing is delayed by | t1−t2 | × Fs, the number of sample steps. Thus, the pseudo sound images in FIG. 3 are 9L ′ and 9R ″, which are the optimum sound image positions.

FIG. 7 shows a state in which the infrared pulse signal α and the ultrasonic wave SR are simultaneously transmitted from the listening position P3 by the remote controller, and the signals are respectively input to the infrared light receiving section 18 and the left and right speakers of the main body. The infrared SL and the ultrasonic signal SR are remote controllers that transmit digital pulse trains for speaker rotation in the same format as other remote control signals.

Next, the processing flow of the microcomputer 10 will be described with reference to FIGS. FIG. 9 shows that the delay circuit 4L,
This is a flow for controlling the 4R. If the speaker rotation switch is detected to be ON in step 30, it is determined in step 31 whether the key is the right (RCH) key or the left (LCH) key. Transition.
In this step 32, it is determined whether or not the right channel has already been delayed. If the delay has not been delayed, that is, if the delay = 0, the delay of the left channel is increased by a certain amount in step 34, and the processing ends. On the other hand, if the right channel has been delayed in step 32, the amount of delay of the right channel is reduced by a fixed amount in step 35, and the process ends.

If it is the right key in step 31, it is determined in step 33 whether or not the left channel has already been delayed. If the delay has not been delayed, that is, if the left channel delay = 0, then in step 36 the right channel has been delayed. The processing is terminated by increasing the delay of the predetermined amount. If it is determined in step 33 that the left channel has been delayed, then in step 37, only the left channel is reduced by a fixed amount, and the process ends.

FIG. 10 is a processing flowchart for delaying the arrival time difference to the earlier one of the left and right channels using ultrasonic waves. At step 38, it is determined whether or not an ultrasonic wave is input. The microcomputer starts time measurement preparation in a timely manner by interrupt processing or the like. When the signal is input, in the next step 39, the time difference between the ultrasonic pulse signals (PR, PL) on the right channel side or the left channel side is measured.
Name it Td. In the next step 40, the T
The number of delay steps is calculated from d. The number of steps is S
Assuming that T and the sampling frequency are Fs, ST = Td ×
The number of steps ST is obtained as Fs. Next, step 4
In step 1, it is determined whether the right channel side ultrasonic signal PR has been input first. If the right channel is first, the delay of the right channel is set to ST sample step delay in step 42, and the left channel delay is set to zero. Finish the process.

If the left channel is input first in step 41, the delay of the left channel is delayed by ST sample steps in step 43, and the process is terminated with the right channel delay set to zero.

FIG. 11 is a flowchart for measuring the arrival time of the left and right channels using infrared rays and ultrasonic waves, and controlling the signal level and the delay amount on the channel side closer to the listener. In step 44, the input of the infrared pulse signal α is detected in a timely manner using the interrupt function of the microcomputer 10, and the input time point is used as a reference. Next, when the right channel ultrasonic pulse PR and the left channel ultrasonic pulse PL are input in step 45, the time from the infrared input is measured, and they are set as t1 and t2. This is as shown in the pulse timing chart of FIG. 8, and in the present example for measuring the timing between the rising and falling of the input pulse, the measurement is performed at the rising.

In the next step 46, the time difference between the left and right ultrasonic pulses PR and PL and the delay step are calculated. Assuming that the time difference is Td, Td = | t1-t2 |,
The delay step ST becomes ST = Td × Fs. In the next step 47, it is determined at times t1 and t2 whether the right channel ultrasonic pulse PR has been input earlier or the left channel ultrasonic pulse PL has been input earlier. If the left channel ultrasonic pulse PL is early, t1> t2, and the routine goes to step 48, where the attenuator amount of the attenuator 13L of the left channel audio signal is calculated by ATR = t2 / t1. In the next step 49, the attenuator amount (ATR value) is set to the attenuator 13L, and the attenuator amount of the right channel audio signal attenuator 13R is set to 1 (neither attenuation nor amplification). In the ST step and set the right channel delay to zero. If the right channel ultrasonic pulse PR is early in step 47, t1 <t2 and the process proceeds to step 51, where ATL = t1 / 1 is set as the attenuator amount of the attenuator 13R of the right channel audio signal.
Calculate t2. In step 52, the attenuator amount (ATL value) is set in the right channel attenuator 13R, and 1 is set in the left channel attenuator 13L.
Is set, and in step 53, the right channel delay amount is set to ST.
Step setting is performed, the left channel delay amount is set to zero, and the process ends.

Next, in the additional signals of the left and right channels, the sound level at the center of the left and right speakers is lowered as described above, so that there is a change in sound quality. In order to improve this, in FIG. 12, a left channel additional signal is taken out from the digital signal input 1L, and one of them is a C attenuator 1
The signal is attenuated and inverted at 9L, and the other enters the adder 20L as an additional signal as it is. On the other hand, the additional signal is also extracted from the right channel system, and one of the additional signals is directly input to the adder 20R as an additional signal, and is added to the signal attenuated and inverted by the left channel C attenuator 19L.

The other is to invert the signal attenuated by the C attenuator 19R and to add the signal of the left channel to the adder 20L. Thereafter, it is connected to the additional signal processing circuit. In the embodiment of FIG. 12, delay circuits 21L and 21R are inserted before the adders 5L and 5R as in the conventional circuit. Let V _{LR be} the same signal on the left and right channels, V _{AL be} the entire audio signal on the left channel, V _{AR be the} entire audio signal on the right channel, V _{L be} the audio signal on the left channel only, and V _{R be} the audio signal on the right channel only. , V _AL = V _L + V _LR V _AR = V _R + V _LR , and the signals in the adders 5L and 5R of the conventional circuit diagram 13 are as follows: V ′ _AL = V _L + V _LR −A (V _R + V _LR ) ∠φ _{= V L -AV R ∠φ + V} LR (1-A∠φ) ───── (3) V 'AR = V R + V LR -A (V L + V LR) ∠φ = V R -AV L ∠φ + V _LR (1−A∠φ) ４ (4) ∴∠φ becomes a phase shift, and in terms of (3) and (4), V _LR (1−A∠φ)
Means that the central audio signal is attenuated.

Attenuator 1 of the embodiment of FIG. 12 of the present invention
When an inverted signal is added using 9L and 19R,-
C (V _L + V _LR ) and -C (V _R + V _LR )
Adder 5L, respectively the output of the 5R _{is, V 3AL = V L + V} LR -A {V R + V LR -C (V L + V LR)} ∠φ = V L (1 + A · C · ∠φ) -AV R ∠ _{φ + V LR {1-A} (1-C) ∠φ} ── (7) V 3AR = V R + V LR -A {V L + V LR -C (V R + V LR)} = V R (1 + A · C・ {Φ) −AV _L {φ + V _LR {1-A (1-C)} φ} (8), and the center audio signal is V _LR {1-A (1-C)} φ ── (9).

On the other hand, taking the left channel signal as an example,
V _{L in} equation (7) (1 + A · C · ∠φ) -AV _{L in} equation (8)
The synthesized signal at the listener position of ∠φ is _VL (1 + A · C · ∠φ) −AV _L ∠φ = V _L ｛1+ (A · CA) ∠φ∠｝ (10), and (9) If the attenuating amount C of the attenuators 19L and 19R is determined such that the phase term of the central audio signal of the formula (1) becomes as small as possible and the phase term of the formula (10) becomes as large as possible, the stereo quality is hardly affected. The effect can be expanded.

[0045]

As described above, according to the audio output circuit of the present invention, a delay circuit is provided for receiving a signal obtained by adding an additional signal to the left and right channel audio signals, and the delay time is set to the left and right listening positions with respect to the left and right channel speakers. In order to control based on the information, after receiving the infrared pulse,
Measure the time until the sound wave is received, and measure the measured time
The delay time of the left and right channels is set based on the
Where the listening position is compared to when only ultrasound is used.
However, an optimal stereo effect can be reliably obtained.

Further, with respect to the additional signal, even if processing such as expansion of the stereo effect can be performed with almost no influence on the sound quality. By controlling the attenuator 21, it is possible to make the central sound forward or backward.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit showing an embodiment of an audio output circuit according to the present invention.

FIG. 2 is a sound image diagram according to a listener position.

FIG. 3 is a sound image diagram when a listener position is on the front right side of the audio equipment.

FIG. 4 is a block-like electric circuit diagram showing another embodiment of the audio output circuit according to the present invention.

FIG. 5 is a diagram showing characteristics of a band-pass filter for ultrasonic detection.

FIG. 6 is a block-like electric circuit diagram showing another embodiment of the audio output circuit according to the present invention.

FIG. 7 is an explanatory diagram of signal arrival by an infrared pulse and an ultrasonic wave when the listener position is on the front right side of the audio equipment.

FIG. 8 is a diagram showing a timing at which an infrared pulse and an ultrasonic wave are input to a microcomputer.

9 is a flowchart showing an operation of the audio output circuit according to the present invention shown in FIG.

10 is a flowchart showing the operation of the audio output circuit according to the present invention shown in FIG.

11 is a flowchart showing the operation of the audio output circuit according to the present invention shown in FIG.

FIG. 12 is a block-like electric circuit diagram showing another embodiment of the audio output circuit according to the present invention.

FIG. 13 is a block diagram illustrating a conventional audio output circuit.

FIG. 14 is a diagram showing a right channel audio signal at a listener position in a conventional audio output circuit.

FIG. 15 is a diagram for explaining how to determine the angle and magnitude of an additional signal vector at a listener position in a conventional audio output circuit.

FIG. 16 is a diagram showing a case where a spread angle of a right channel speaker in a conventional audio output circuit is 30 °.

FIG. 17 is a diagram showing a case where a spread angle of a right channel speaker in a conventional audio output circuit is 0 °.

FIG. 18 is a flowchart provided for describing the operation of a conventional audio output circuit.

[Explanation of symbols]

 2L, 2R Attenuator for left and right channel system 3L, 3R Phase control circuit for left and right channel system 4L, 4R Delay circuit for left and right channel system 5L, 5R Adder for left and right channel system 9L, 9R Speaker for left and right channel system 10 Microcomputer 13L, 13R Band pass Filter 18 infrared pulse receiver

Claims (4)

(57) [Claims] 1. A left-channel audio signal is extracted as an additional signal, the level is controlled and the phase is inverted, and a right-channel audio signal and a right-channel audio signal are extracted as an additional signal to control the level. A sound output circuit for inverting the phase and adding each of the left and right channel signals to the left channel signal ;
The ultrasonic and infrared pulses transmitted from the controller
That is, the speakers or speakers of the left and right channels receiving ultrasonic waves.
An ultrasonic receiving element attached to a peaker section;
An infrared light receiving unit for receiving a line pulse;
From receiving light to receiving ultrasonic waves in the left and right channels
Measure the time and use the difference data between the measured left and right time
The delay time of the left and right channels is set based on
An audio output circuit provided with control means for controlling an extension circuit . 2. A left and right channel based on the measured time.
2. The audio output circuit according to claim 1, wherein the gain of the channel is adjusted . 3. An ultrasonic wave using left and right channel speakers.
While the speaker's bandpass filter
The characteristics and the ultrasonic frequency can be adjusted for the speaker drive output amplifier.
Based on the speaker frequency and speaker impedance.
The audio output circuit according to claim 1, characterized in that a constant. 4. A left-channel audio signal is extracted as an additional signal, and before the level and phase are controlled, the right-channel audio signal is attenuated by passing through an attenuator, and a signal obtained by inverting the extracted signal is added to the left-channel audio signal. A means for adding to a signal is provided, and a means for controlling a level and a phase of a signal output from the adding means, inverting the phase and adding the inverted signal to a left channel signal is provided. An additional means for extracting an additional signal, attenuating the extracted left-channel audio signal through an attenuator before controlling the level and phase, and adding the inverted signal to the right-channel additional signal; Means for controlling the level and phase of the output signal, inverting the phase and adding it to the right channel signal,
An audio output circuit characterized by controlling the spread of left and right sounds.