JPH06303699A - Sound field reproduction device - Google Patents

Abstract

PURPOSE:To allow only a font speaker of a listener to provide a reflecting sound between a front side and a side direction or between the front side and rear side without arrangement of a real speaker. CONSTITUTION:Two signals ML(t), MR(t) to be reproduced from L and R channels are inputted respectively to input terminals 2, 3, and received by reflecting sound generating circuits 11-14 forming a reflecting sound and a reverberation sound. The output of the circuits is given to FIR filters 15-18 so that sound is localized at a left side or a left rear side hLR(n) and hLL(n) of the FIR filters 17, 18 indicate impulse response in the time domain of a head transfer function so as to localize the sound to a left side or a left rear side when front speakers 4, 6 are in use and similarly hRR(n) and hRL(n) of the FIR filters 15, 16 indicate impulse response in the time domain of a head transfer function so as to localize the sound to a right side or a right rear side. Output signals from the FIR filters 15-18 are inputted to adders 19, 20, their output signals are given to the speakers 4, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound field reproducing apparatus for reproducing a realistic sound in AV (audio / visual) equipment.

[0002]

2. Description of the Related Art In recent years, VTRs have been used in the video and audio fields.
In order to enjoy movies at home due to the widespread use of sound, there is a demand for large-screen and realistic sound reproduction, and the development of hardware corresponding thereto is desired.

Particularly in the sound of VTR movie software, a Dolby surround system in which a speaker is arranged laterally or rearward (or a combination thereof) for reproduction as in a movie theater. Is widespread.

In addition, as for the high-definition sound reproduction system currently being developed in Japan, it is likely that the 3-1 system 4-channel stereo reproduction of front 3ch and rear 1ch will be adopted.

FIG. 7 is a block diagram of a conventional sound field reproducing apparatus for reproducing sound with a realistic sensation.

In FIG. 7, the viewer 8 is connected to the input terminals 2 and 3.
The signal ML (t) (t represents continuous time, indicating that the signal is a time function, and so on) to be reproduced from the Lch viewed from the point of view and the Rch viewed from the viewer 8. The desired signal MR (t) is input, and speakers 4 and 6 are connected to these input terminals 2 and 3. Further, the two signals are added at a certain ratio by an adder 7
Are added and output to the speaker 5 arranged in the front center of the viewer 8.

The two signals ML (t) and MR (t) are
A surround signal to be reproduced from the rear or the side by processing these two signals (reverberation sound or reflected sound generated when the input signal is radiated from a speaker in a normal room) and The surround signal S (t) that is input to the surround creation circuit 1 that creates a signal S (t) of a reverberant sound or a reflected sound that is called, and the output surround signal S (t) is two speakers 9, 10 arranged on the left and right sides of the viewer. (The signals ML (t) and MR (t) usually refer to what is called a stereo signal. In addition to the surround signal S (t) described above, these are also called main signals). .

The operation of the sound field reproducing device configured as described above will be described with reference to the drawings. First, in the configuration of FIG.
2ch signals ML (t) and MR normally reproduced from VTR
(t) is input to the surround signal creating circuit 1, and the surround signal S (t) such as reverberation or reflected sound is created by performing calculations such as subtraction and addition on these signals. The main signals ML (t) and MR (t) are reproduced from the speakers 4 and 6, respectively, and the surround signal S (t) is reproduced from the speakers 9 and 10. Further, the main signals ML (t) and MR (t) are added at a predetermined ratio by the adder 7, and the added signal is reproduced from the speaker 5.

Further, by using a decoder called a Dolby surround processor or the like instead of the surround signal generating circuit 1, it is possible to encode a movie etc. recorded on 2ch for a Dolby surround. From the acoustic signal, a surround signal S (t) optimally created on the screen and reproduced from the rear and a signal reproduced from the front center are obtained, and the surround signal S (t) is obtained from the speakers 9 and 10. The center signal may be reproduced from the speaker 5. The surround signal S (t) should be emitted, for example, around the room projected on the screen (reflection sound or reverberation sound) or behind the viewer when the viewer is in the screen. It is added as a sound.

As described above, as compared with the 2ch stereo reproduction system which normally uses two front speakers, the sound that was heard from the front or the sound that was not heard was surround sound from the side or the rear. Is added, it becomes possible to reproduce sound with a sense of reality. Also, in this system, a center speaker is arranged in the front, and the main signals ML (t) and MR (t) are added at an appropriate level and reproduced, thereby clarifying the localization of the sound image in the front. I have to.

[0011]

However, in the above-mentioned configuration, a speaker which is a sound reproducing means such as a side or a rear is required to reproduce the surround signal S (t), and There was a problem that a space for placing this speaker was necessary.

In consideration of the above problems of the prior art, the present invention allows the reproduced sound, including the reflected sound, to be heard as a sound from a place other than the reproduction place of the sound reproduction means, thereby providing a side or rear speaker. It is an object of the present invention to provide a sound field reproducing device capable of reproducing sound with a sense of presence without using a sound field.

[0013]

According to the present invention, an input means for inputting a sound signal, a reflected sound producing means for producing a reflected sound or a reverberant sound by adjusting a delay time and an amplitude of the sound signal, and one reflection A branching unit that branches the output signal of the sound creating unit into at least two, and a sound signal that is input to the branching sound signal and radiated to the viewer is heard as a sound from any direction. At least 2 to adjust amplitude and delay time
One adjusting means, the output signal of the other reflected sound creating means and the output signal of each adjusting means are input, and an adding means for adding them at a certain ratio, and a sound signal connected to the adding means to the viewer as sound. It is a sound field reproducing device including sound reproducing means for reproducing.

[0014]

According to the present invention, the delay time and the amplitude of the sound signal input by the two reflected sound creating means are adjusted to create a reflected sound or a reverberant sound, and the output signal of one reflected sound creating means is adjusted. In the means, the amplitude and delay time of the sound signal are adjusted so that the sound radiated to the viewer can be heard as sound from any direction, and the output signal of the other reflected sound creating means and the output signal of the adjusting means are adjusted. By adding the sound signal as a sound to the viewer by adding the sound signals by the adding means at a certain ratio, the sound to be reproduced can be heard as a sound from a place other than the reproduction place of the sound reproducing means including the reflected sound. It is possible to reproduce sound with a sense of reality without using an external speaker such as a side speaker.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a sound field reproducing apparatus according to the first embodiment of the present invention. Lc as seen from viewer 8
The two signals, that is, the signal ML (t) to be reproduced from h and the signal MR (t) to be reproduced from Rch as viewed from the viewer 8 are input to the input terminals 2 and 3, respectively, and then two signals each. Reflected sound generation circuit 11, 12, 1 which is branched into two and simulates a sound field of a hall or the like to generate a reflected sound or a reverberant sound.
3 and 14 are input. The outputs of the reflected sound producing circuits 12 and 13 are further branched into two signals, respectively, and the head related transfer function is digitally processed in the time domain so that the sound is localized to the left side or the left rear side with respect to the viewer 8. FIR filters 15, 16, 17, 1 which are adjustment means for performing
8 is input. HRR of FIR filters 15 and 16
(n) and hRL (n) (n is actually nT, T is the sampling time, but is generally omitted by omitting T. Also, n is a natural number, and so on) On the other hand, when the front speakers 4 and 6 are used, it is an impulse response that represents the head related transfer function in the time domain such that the sound is localized to the right side or the right side. In addition, the FIR filters 17, 1
8 hLL (n) and hLR (n) are head-related transfer functions that cause the sound to be localized leftward or leftward when using the speakers 4 and 6 in front of the viewer 8. It is an impulse response expressed in the time domain.

The output signals of the FIR filters 15, 16, 17, 18 are input to adders 19, 20. Further, the output signals of the reflected sound producing circuits 11 and 14 are also input to the adders 19 and 21, and the outputs of the respective adders are the speakers 4 and 6.
It is connected to the.

The operation of this embodiment will be described with reference to FIG. Normally, stereo signals ML (t) and MR (t) reproduced from a VTR or the like are input to the input terminals 2 and 3, and thereafter, reflected sound producing circuits 11 and 12 and reflected sound producing circuit 1 respectively.
3 and 14 are input. Then, the reflected sound creating circuits 11, 12 and 13, 14 are paired to create a reflected sound or a reverberant sound for simulating a sound field such as a hall.

2A and 2B schematically show the impulse responses (reflected sound series) of the reflected sound producing circuits 11 and 12, respectively, with the horizontal axis representing time and the vertical axis representing amplitude. ing. As will be described later, it is considered that the output signal of the reflected sound creating circuit 12 is localized to the right side or the right rear side other than the speakers 4 and 6 by using the FIR filters 15 and 16.
As shown in FIGS. 2A and 2B, the delay time and the amplitude of the reflected sound are set. For example, the output signal of the reflected sound producing circuit 12 is electrically processed by the speaker 25 as shown in FIG.
Assuming that the sound can be played from the position (it is not the speaker actually placed and is called a virtual sound source),
When the delay time and the amplitude are set as in (a) and (b), the output signal of the reflected sound creating circuit 12 is output from the speaker 25, and the output signal of the reflected sound creating circuit 11 is the speaker 4.
Is output from the position.

At this time, sound images are synthesized due to the human auditory nature, and it is felt that a reflected sound is emitted from the position shown in FIG. 2C ("spatial sound": Jen Brauert et al., See Kashima Publisher). Here, in FIG. 2C, the reflected sound is displayed as a vector, and its length corresponds to the loudness of the sound. Moreover, the reflected sound is shown in FIG.
It occurs with a time delay as shown in (b). Of course, in order to synthesize the reflected sound between the speaker 4 and the speaker 25, not only the amplitude difference of the reflected sound emitted from both speakers but also the time difference may be used. Further, these reflected sounds are obtained by actual measurement in a hall or simulation using a sound ray method or the like.

FIG. 3 is a diagram for explaining the reflected sound producing circuits 11, 12, 13, and 14 for producing this reflected sound. Figure 3
, 26 is an input terminal, 27 is a delay device for delaying by the time indicated by τi (i is Safux, and so on),
28 is a multiplier (called a tap) that multiplies a value called a tap coefficient indicated by X (i) by the signal output from each delay device, and 29 is an adder that sums the signals output from each tap. , 30 are output terminals. This display shows the case where a digital signal is used, and when dealing with an analog signal, this reflected sound producing circuit 11, 12, 13,
Before being input to 14, it needs to be converted to a digital signal by an A / D converter (in this embodiment,
This A / D converter is omitted in the part where analog-to-digital conversion is required, and the same applies hereinafter).

The reflected sound producing circuits 11, 12, 13, 1
Reference numeral 4 denotes FIR filters 15, 16, 17, 18 described later.
Similarly to the above, it is configured by the delay device 27 and the tap 28 as described above, and in this case, the impulse response (reflected sound sequence) as shown in FIG. 3B is obtained. Conversely, FIG.
When it is desired to set the reflected sound as shown in (b), the amplitude Xi and the delay time τi are set to the tap and the delay device in FIG. 3A. This is actually composed of a DRAM (dynamic random access memory) and a DSP (digital signal processor).

In the reflected sound producing circuits 13 and 14, the delay time and amplitude of the reflected sound are set so that the reflected sound is similarly synthesized to the left.

Next, the output signals of the reflected sound producing circuits 12 and 13 are respectively branched into two, and as described above, the impulse response hRR (n) that localizes the sound to the right side or the right rear side of the viewer 8. , HRL (n) as tap coefficients, and FIR filters 17 having impulse responses hLR (n) and hLL (n) as tap coefficients that localize sounds to the left or left rear of the viewer 8. , 18 and a convolution operation is performed.

Now, a method for virtually locating a sound image to the left or right side of the viewer using the speakers 4 and 6 placed in front will be described with reference to FIG. In FIG. 4, h1 (t) is the head at the position of the left ear of the speaker 6 and the viewer 8 (accurately, the position of the eardrum, but in the case of measurement, the position of the ear canal entrance, and so on). A transfer function (hereinbelow, referred to as an impulse response because it is expressed in the time domain), h2 (t) is an impulse response at the position of the speaker 6 and the right ear of the viewer 8, and h3 (t) is Impulse response at the position of the speaker 4 and the left ear of the viewer 8, h4 (t) is the impulse response at the position of the speaker 4 and the right ear of the viewer 8, and 31 is actually on the left side of the viewer. Placed Speed
H, h5 (t) is the impulse response at the position of the speaker 31 and the left ear of the viewer 8, and h6 (t) is the impulse response at the position of the speaker 31 and the right ear of the viewer 8. Other parts having the same functions as those in FIG. 1 are indicated by the same numbers and symbols.

In such a structure, when the signal S (t) is radiated from the speaker 31, the sound reaching the ear of the viewer 8 is the left ear L (t).

[0027]

[Equation 1]

In the right ear R (t),

[0029]

[Equation 2]

Is expressed (in practice, the transfer function of the speaker itself is multiplied, but this is ignored, and it is considered that the transfer function of the speaker etc. is included. May be).

Further, the impulse response and the signal S (t) are considered as digital signals whose time is discrete, and L (t) → L (n) R (t) → R (n) h5 (t) → h5, respectively. Expressing (n) h6 (t) → h6 (n) S (t) → S (n), (Equation 1) and (Equation 2) are as follows.

[0032]

[Equation 3]

[0033]

[Equation 4]

Similarly, the signal S (t) is changed by the speakers 9, 1
The sound radiated from 0 and reaching the viewer 8 is

[0035]

[Equation 5]

In the right ear,

[0037]

[Equation 6]

[0038] Assuming that sound can be heard from the same direction if the head-related transfer functions are equal (this assumption is generally correct),

[0039]

[Equation 7]

From

[0041]

[Equation 8]

[0042]

[Equation 9]

From

[0044]

[Equation 10]

HLL (n) and hLR (n) may be determined so that For example, if (Equation 8) and (Equation 10) are rewritten in the frequency domain expression, the convolution operation is changed to multiplication as in (Equation 11) and (Equation 12), and then each impulse response is transmitted by FFT. It becomes a function.

H1 (n) = FFT (h1 (n)) H2 (n) = FFT (h2 (n)) H3 (n) = FFT (h3 (n)) H4 (n) = FFT (h4 (n) ) H5 (n) = FFT (h5 (n)) H6 (n) = FFT (h6 (n)) HLL (n) = FFT (hLL (n)) HLR (n) = FFT (hLR (n)) , FFT () represents FFT

[0047]

[Equation 11]

[0048]

[Equation 12]

Transfer function of FIR filter HLL (n), HRR (n)
Since the values other than the two are obtained by measurement, the transfer functions HLL (n) and HRR (n) of the FIR filter can be obtained from these two expressions as follows.

[0050]

[Equation 13]

[0051]

[Equation 14]

HLL (n), hLR determined in this way
(n), hLL (n) is used for the signal S (n) and the signal output from the speaker 6, and hLL (n) is used for the signal output from the speaker 4.
By convolving and radiating with LR (n), it is possible for the viewer 8 to feel that sound is coming from that direction without actually sounding the rear speaker 31.

The actual convolution operation is 15,
FIR filters 16, 17, and 18. This FIR
The basic structure of the filter is shown in FIG. In FIG.
32 is an input terminal for inputting a signal, 33 is a delay element for delaying the signal by τ, 34 is a multiplier for multiplying a value called a tap coefficient represented by h (n) by the input signal, and 35 is an addition of the input signals And an adder 36 for outputting a signal.

As described above, in general, such FI
As the R filter, a DSP or a dedicated LSI that performs multiplication and addition at high speed is used. An impulse response h (n) (n: 0 to N-1, where N is a required impulse response length) is set in the multiplier 34 as a tap coefficient, and an analog signal is input to the delay element 33. A delay time corresponding to the sampling frequency when converting to a digital signal is set, and the convolution operation as shown in (Equation 3) and (Equation 4) is performed by repeating multiplication and addition and delay with respect to the input signal, respectively. To execute. Since this is the case of a digital signal, the A / D converter that converts an analog signal into a digital signal before this FIR filter and the D / A converter that converts a digital signal into an analog signal behind this FIR filter are actually used. Although necessary, it is omitted in FIG.

As described above, the FIR filters 15 and 16 virtually create speakers on the right side or the rear of the viewer 8, and similarly, the FIR filters 17 and 18 create virtual speakers on the left side and the rear. create. And this F
By adding the output signals of the IR filters 15, 16, 17, and 18 by the adders 19 and 20 and radiating them from the speakers 4 and 6, it is possible to simultaneously create virtual speakers on the left and right sides for the viewer 8. Therefore, as described above, the reflected sound can be synthesized and presented between the virtual speaker and the speakers 4 and 6.

FIG. 6 is a block diagram showing a sound field reproducing apparatus according to the second embodiment of the present invention. Lch as seen from viewer 8
The signal ML (t) to be reproduced from Rch and the signal MR (t) to be reproduced from Rch as viewed from the viewer 8 are
The signals are input to the input terminals 2 and 3, and then branched into two and input to a surround circuit 37 that creates a reflected sound or a reverberant sound that simulates a sound field such as a hall. And
The output signal of the surround circuit 37 is divided into two and divided into three.
It is input to a delay device that delays the signal for a certain time of 8, 39, and its output signal is branched into three,
FIR filters 15 and 16 which are adjusting means for digitally processing the head related transfer function in the time domain so that the sound is localized rightward or rearward with respect to the viewer 8;
Input to FIR filters 17, 18 and adders 40, 41 which are adjusting means for digitally processing the head related transfer function in the time domain so that the sound is localized leftward or leftward with respect to the viewer 8. To be done. FIR filter 15,
MR (t) which is the output signal and the input signal of 16 and 17, 18
And ML (t) and the output signals of the delay devices 38 and 39 described above are input to adders 40 and 41. And the adders 40, 4
The output signal of 1 is connected to the speakers 4 and 6.

The operation of this embodiment will be described with reference to FIG. Normally, stereo signals MR (t) and ML (t) reproduced from a VTR or the like are input to input terminals 2 and 3, respectively.
Then it is input to the surround circuit 37, where ML
By calculating the sum or difference of (t) and MR (t), a simple reflected sound or reverberant sound that simulates the sound field of a hall or the like is created.

Next, the output signal of the surround circuit 37 is
Impulse response hRR (n) that localizes the sound to the right or rear of the viewer 8 after being branched into two and input to the delay devices 38 and 39 for delaying by a certain time and being delayed as described above. FIR filters 15 and 16 having hRL (n) as tap coefficients, and FIR filters 17 having impulse responses hLR (n) and hLL (n) that localize sounds to the left or left of the viewer 8 as tap coefficients, It is input to 18 and a convolution operation is performed. Then, the FIR filter 1
The output signals of 5 and 16, the output signals of the FIR filters 17 and 18, the output signals of the delay devices 38 and 39, and the input signals MR (t) and ML (t) are added by adders 40 and 41, and the speaker 4 , 6 is emitted.

The output signals of the FIR filters 15 and 16 are
The sound image of the output signal of the delay device 38 is localized in the direction of the speaker 4 with respect to the viewer 8 as a sound image is localized to the right side or the right rear side of the viewer 8. Further, the output signals of the FIR filters 17 and 18 are temporally displaced from the output signals of the FIR filters 15 and 16 and the output signal of the delay device 38, and are localized as a sound image on the left side or the left rear side of the viewer 8. (The output signals of the FIR filters 15 and 16 are also output with a time lag from the output signal of the surround circuit 37).

Similarly, the sound image of the output signal of the delay device 38 is
The output signals of the FIR filters 15 and 16 and the output signal of the delay device 38 are temporally displaced and localized in the direction of the speaker 6. As described above, one of the sound images of the output signal of the surround circuit 37 is emitted from the speaker 4 direction and the right side (or the rear side) of the viewer 8.
The output signal from 7 is localized. The other is that the output signal from the surround circuit 37 is localized during this period by sounding from the left side (or rear side) of the speaker 6 and the viewer 8. Since the output signal of the surround circuit 37 is temporally shifted by the delay devices 38 and 39 and separated into two, the sound image can be localized at the above two positions.

The input signals MR (t) and ML (t) have their sound images localized between the speakers 4 and 6, respectively, and the output signal of the surround circuit 37 described above is localized to the left and right of the viewer 8. You can reproduce sound with a very realistic feel.

In the second embodiment, one surround circuit 37 is provided to synthesize a sound image between a real speaker and an imaginary speaker (almost in the center) with reflected sound or the like.
As in the reflected sound creating circuits 11, 12, 13, and 14 of the above embodiment, the reflected sound or the like is created in a pair with respect to one signal, so that the reflected sound or the like is synthesized at an arbitrary position between the real speaker and the imaginary speaker. It is possible to

On the contrary, in the first embodiment, the reflected sound producing circuits 11, 12, 13 and 14 are processed by one for each signal as in the surround circuit 37 of the second embodiment. Although the effect is slightly reduced, the circuit scale can be reduced.

[0064]

As described above, according to the present invention, the delay time and the amplitude of the sound signal input by the two reflected sound creating means are adjusted to create a reflected sound or a reverberant sound, and one reflected sound creating means is further provided. In the adjusting means, the amplitude and delay time of the sound signal are adjusted so that the sound radiated to the viewer can be heard as sound from any direction, and the output signal of By adding the output signals of the adjusting means by the adding means at a certain ratio and reproducing the sound signal as a sound to the viewer, the sound to be reproduced is heard as a sound from a place other than the reproduction place of the sound reproducing means including the reflected sound. Therefore, it is possible to reproduce sound with a sense of reality without using an external speaker such as a side or a rear.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an impulse response of a reflected sound creating circuit.

FIG. 3 is a diagram illustrating a reflected sound creating circuit.

FIG. 4 is a diagram illustrating a method of localizing sound to the side or the rear by a speaker arranged in the front.

FIG. 5 is a diagram illustrating an FIR filter.

FIG. 6 is a block diagram of a second embodiment of the present invention.

FIG. 7 is a block diagram of a conventional sound field reproducing device.

[Explanation of Codes] 2, 3 Input Terminals 4 Rch Speaker 6 Lch Speaker 8 Viewers 11, 12, 13, 14 Reflected Sound Creating Circuit 15, 16, 17, 18 FIR Filter 19, 20 Adder

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area H04R 3/12 7346-5H

Claims (1)

[Claims] 1. An input means for inputting a sound signal, and at least two reflected sound creating means for creating a reflected sound or a reverberant sound by adjusting a delay time and an amplitude of the sound signal input to the input means. The branching means for branching the output signal of the reflected sound creating means into at least two, and the sound radiated to the viewer by inputting each of the branched sound signals is heard as a sound from an arbitrary direction. Add at least two adjusting means for adjusting the amplitude and delay time of the sound signal, the output signal of the other reflected sound creating means and the output signal of each adjusting means, and add them at a predetermined ratio. A sound field reproducing apparatus comprising: means and sound reproducing means that is connected to the adding means and reproduces a sound signal as a sound to a viewer.