JPS6027236B2 - 4 channel headphone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to four channels (CH
) 4C to play the program source and listen to it with headphones
Regarding the H headphone device, the present invention provides a headphone device in which the sound image is localized outside the head with a sense of distance, as if the four program sources were being received by four speakers in the room while listening to the headphones. It is.

Figure 1 shows a situation in which a 4CH program source such as a cord or magnetic tape is received indoors using four speakers in a typical front and back 2-2 arrangement.
In the figure, 1 is the front right speaker, 2 is the front left speaker, 3 is the rear right speaker, 4 is the rear left speaker, and 5 is the front right speaker.
6 is the right ear of the listener 5, and 7 is the left ear of the listener. The direct sound path from the right front speaker 1 to the right ear 6 of the listener 5 is la, and the direct sound path reaching the left ear 7 is lb.
Direct sound paths 2a and 2b are shown for the left front speaker 2, 3a and 3b for the right rear speaker 3, and 4a and 4b for the left rear speaker 4, respectively. Therefore, as can be seen from FIG. 1, in addition to the direct sound la from the speaker 1, the direct sounds 2b, 3a, and 4b from the speakers 2, 3, and 4 are also mixed into the right ear 6 of the listener 5, and similarly the left ear In addition to the direct sound 2a of speaker 2, direct sound lb of speakers 1, 3, and 4 is displayed on 7.
, 3b, and 4a are also included in A. Furthermore, there is a time difference between the two direct sounds reaching the listener's right and left ears from each speaker, which is caused by the distance and angle from the speaker to the listener. That is, the direct sounds lb, 2b, 3b, 4b of each speaker in FIG. 1 are la, 2a, 3a, 4a.
There is a fact that there is a slight time delay with respect to each direct sound of B. Furthermore, the transmission frequency characteristics from each speaker to the eardrums of both ears of the listener differ mainly due to the difference in the angle of incidence of the sound waves reaching the listener's skull and both pinnaes. This characteristic difference can be investigated using an artificial head microphone, and an example of its measurement is shown in FIG. Figure 2 a
Figure 2 is an example of measuring a speaker with a flat frequency response at a distance of 1 from the artificial head microphone, with the sound reception angle of incidence at 45o to the front right.
(This is an example of measurement at 45 o's rear). It can be seen that there is a difference in the transmission frequency characteristics of both a and b from frequencies around 500 Hz and above. Another thing to consider in Figure 1 is the reflected sound (indirect sound) from the entire wall of the room. In actual speaker listening, the walls 8a, 8b,
In addition to 8c and 8d, there are countless paths of reflected sound (indirect sound) from the floor and ceiling. Due to the nature of reflected sound, these reflection costs arrive at both ears later than direct sound, and are phase shifted each time they are reflected from walls, and due to the acoustic asymmetry of the room, they reach both ears. Reflected sounds often have a phase difference. Also, as a characteristic of reflected sound, when reflection occurs,
There is a fact that the higher the frequency, the greater the amount of absorption.○ However, it can be seen that the conventional 4CH headphone listening system has problems regarding the four points A, B, C, and D mentioned above. The conventional 4CH headphone listening system will be described below. FIG. 3 shows a conventional example of a 4CH headphone listening system.

In Figure 3, 9 is used to connect 4 to 4, such as a cord or magnetic tape.
CH program source playback device, 1 Kawama headphone listener, 11 and 12 are the right ear and left ear of the headphone listener, 13 is the headphone right unit, 14 is the headphone left unit, 15 and 16 are built in the headphone right unit. The electro-acoustic transducers 17 and 18 shown above are also electro-acoustic transducers built into the headphone unit. The first thing that can be seen from FIG. 3 is that the signal emitted from the electro-acoustic transducer 15 only reaches the right ear 11 and does not reach the left ear 12. Further, the signal sound emitted from the electro-acoustic transducer 17 only reaches the left ear 12 and does not reach the right ear 11. The same applies to electro-acoustic transducers 16 and 18. Therefore, the localization stage of the sound image by the left and right electro-acoustic transducers I5 and 17 is, for example, point A, and the localization stage of the sound image by the left and right electro-acoustic transducers I5 and 17 is, for example, point B. This is no different from traditional headphone listening, and the sound image is localized in your head. Next, the sense of front and back in the 4CH speaker reception is shown in Figure 3. In the conventional system, the short distance between the electro-acoustic transducers 16 and 16, or 17 and 18, which are placed close to both ears of the listener 10, is shown in Fig. 3. , it has to be judged based on the interval, and the sense of front and back is very poor. In addition, the headphones are designed so that the transmission frequency characteristics from each electro-acoustic transducer to both ears are flat, and the distance to the sound source and the sound receiving incident angle as shown in Figure 2a and The characteristic that is uniquely determined by is not given. Furthermore, since there is no signal path for mixing from one CH to the other, there is no interaural time difference that contributes to the sense of direction, and, of course, there is no indirect sound component at all. Therefore, it can be seen that the 4CH headphone listening system as shown in Fig. 3 is no different from the conventional headphone listening method from an acoustic point of view. In view of the above-mentioned drawbacks of the conventional day-to-day headphone listening system, the present invention has been developed in such a way that, while conventional day-to-day listening is performed using a certain day-to-day headphone system, the localization of each layer on the day is the same as the 4CH speaker reception shown in FIG. To provide a 4CH headphone device characterized in that a listener can recognize the localization of a sound image outside the head with a sense of distance and direction, and does not get tired even when listening to headphones for a long time.

Embodiments of the present invention will be described in detail below with reference to the drawings. In FIG. 4, 21 and 22 are input terminals to which the front two signals of the 4CH stereo reproduction signal from the reproduction device are applied, 23 and 24' are input terminals to which the rear two signals are applied, and 25 are input terminals to which the rear two signals are applied. , 26, 25', 26' are adders, 27, 27
' is a delay circuit, 28, 28' are feedback circuits, 29, 29'
is a variable attenuator, and 30 and 30' are phase shift circuits. Also,
31a', 31b', 32a', 32b', 33a',
33b', 34a', 34b' are low pass filters, respectively, 35, 36, 37, 38, 35', 36
', 37', and 38' are adders, respectively. The electric circuit that creates the indirect sound signal will be explained below. input terminal 21,
The two forward signals applied to 22 are added by an adder 25,
The signal reaches the adder 26 and becomes an input signal to the delay circuit 27. A portion of the output signal delayed via the delay circuit 27 is added to the input signal by the adder 26 via the feedback circuit 28. The output signal of the delay circuit 27 is adjusted to an appropriate signal level by a variable attenuator 29 and divided into two parts, one of which is directly input to the low-pass filters 32a' and 32b', and the other is input to the phase shifter 30. and low pass filter 31, 31b
′ becomes the input signal. Further, the two rear signals applied to the input terminals 23 and 24 also pass through the same electrical path as the two front signals. Here, to explain the role of each circuit part of the indirect sound signal generation circuit, the delay circuits 27, 27
' is used to obtain a time delay peculiar to reflected sound, and the delay time can be obtained from several S to several tens of S. Feedback circuit 2
8 and 28' are circuits for simulating multiple reflections of reflected sound, and by controlling the gain of this circuit, the time from the initial delay time to the final delay time of the delay circuit can be freely changed. can. The phase shifters 30 and 30' are used to create this phase difference, since the phase of the sound wave reaching the listener differs due to the asymmetry of the room and the phase shift of the reflected sound when it is reflected from the wall. This is the circuit. Low pass filter 31a', 31b', 32a', 32b',
33a', 33b', 34a', and 34b are for cutting the Takagi frequency component of the delay circuit output signal, since the Takagi frequency component of the reflected sound is absorbed by the wall surface during reflection. That is, as mentioned above, the frequency band range in which the direction of the sound source shown in Fig. 2 is characterized is approximately 450° to the right.
Since the K ratio is approximately 1350 Hz, the phase shifter 30,
30', low pass filters 31a' to 34, 31b
' to 34b' have the following characteristics. First, the frequency-phase amount transition characteristic of the front phase shifter 30 is such that the phase shift amount f is l for the input signal in a frequency band below approximately z.
It has a characteristic that changes within the range of fl.

On the other hand, the rear phase shifter 30' is also interposed for the purpose of imparting a pseudo effect similar to the front one, but its frequency-phase shift amount r is within a frequency band of about Hz or less,
The amount of phase shift is different from that for the front so as to maintain the f- rIS of l. As a result of this configuration, by performing phase difference processing on the two front and rear indirect blue signal outputs, it is possible to obtain four pseudo indirect green signal outputs, and the sound image outside the head effect of this headphone device can be reproduced in each of the four channel signals. It is something that can be improved. Next, the low pass filter 31
A' to 34 and 31b' to 34b' are provided for the purpose of setting four pseudo independent indirect green signals for each signal in the sound arrival direction based on the listener's intellect.

Regarding the distance perception effect of sound images caused by direct sound and indirect green signals, it is generally known that there is an incident direction of indirect sound that gives the maximum sense of distance.

On the other hand, the direction of the sound is determined by the absolute frequency characteristics of the listener's binaural blue signal.
It is determined by the relative frequency characteristic difference and the relative time difference between both ears. From these facts, the cutoff frequency of the front low-pass filter 31 and 31b' must be approximately H.
Near z, low-pass filter for rear - 33 and 33b'
is set around the approximate secretion ratio, and the characteristics of the binaural characteristics as shown in Figure 2 a and b are added to realize the identification of four indirect sound directions.As a result, the sound image of this headphone device is This enhances the extra-head effect in each of the four channel signals. In addition, the other two sets of low-pass filters 32 and 32b'
, or 34a' and 34b' have the same structure as each of the low-pass filters 31a' and 31b', or 33 and 33b'. In addition, since it is necessary to set the direction of indirect sound for signals that do not pass through the phase shifters 30, 30', eight low/gas filters 31 to 34a'
, 31b' to 34b' are all indispensable, and if these low-pass filters are not interposed, a sufficient sound image head feeling cannot be obtained, and they are indispensable for the structure of the present invention.

As mentioned above, the 4CH stereo signal applied from the input terminal is converted into a reflected sound (indirect sound) signal that approximates the reflected sound that occurs when using a speaker in an actual room by the function of these electric circuits. Adders 35, 36, 37, 38
Then, 35', 36', 37', and 38' are reached.

Next, the direct green signal path will be explained according to FIG. In this embodiment, it is assumed that the positions at which sound image localization is recognized are 450 degrees front and back and a distance of 1. Therefore, input terminal 2
The transmission frequency characteristic from No. 1 to the eardrum of the right ear of the headphone listener must be equal to the characteristic shown by the solid line a in FIG. 2. Furthermore, the transmission frequency characteristic from the input terminal 21 to the eardrum of the left ear of the headphone listener must be equal to the characteristic shown by the dotted line a in FIG. 2. The same thing can be said about the transmission characteristics from the input terminal 22 to the eardrums of both ears of the headphone listener. Next, considering the rear side, the transmission frequency characteristic from the rear input terminal 23 to the eardrum of the headphone listener's right ear is the same as the solid line in Figure 2b, and the transmission frequency characteristic from the rear input terminal 23 to the eardrum of the headphone listener's left ear is the same as the solid line in Figure 2b. The frequency characteristics must be equivalent to the dotted line in Figure 2b. Based on the above-mentioned reason, a correction circuit that adjusts the signal frequency characteristics applied from each input condition to the transmission frequency characteristics shown in FIG. 31a, 31b in the figure
, 32a, 32b, 33a, 33b, 34a, 34b, and 39, 40, 39', 40' are delay circuits.

41, 42, 41', 42' are adders, 43, 44 are intensifiers, 45 is the electroacoustic transducer on the right side of today's headphones,
46 is an electroacoustic transducer on the left side of the headphones.

Here, the electroacoustic transducer 45 is connected to the input terminals 21 and 22.
The flow of signals up to and including 46 will be explained.

The flow of these two signals presents the recognition of sound image localization similar to the state in which the listener is listening through the speakers 1 and 2 in FIG.
In FIG. 4, the front right signal applied from the input terminal 21 reaches the adder 35 via the correction circuit 31a, mixes with the reflected blue signal arriving via the low-pass filter 31a', and then passes through the adder 41. The reflected sound is amplified by the intensifier 43 and applied to the electroacoustic transducer 45 on the right side of the headphones, and at the same time reaches the adder 36' via the other correction circuit 31b, and reaches the reflected sound via the low-pass filter 31b'. After being mixed with the signal, the delay circuit 39 delays the binaural time difference, and the signal reaches the intensifier 44 via the adders 42 and 41'. Electroacoustic transducer 46 on the left side of the telephone
is applied to At this time, due to the action of the two signals applied to both electroacoustic transducers of the headphones, the headphone listener can perceive the sound image localization outside the head, with a sense of distance, to the front right 45o. Similarly, the left front signal applied to the input terminal 22 reaches the adder 38 via the correction circuit 32a, and the 32
a′ and mixed with the reflected blue signal arriving via adder 42,
41' and an intensifier 44 to the electroacoustic transducer on the left side of the headphones. At the same time, the signal passing through the correction circuit 32b and the reflected blue signal passing through the low-pass filter 32b' are mixed in an adder 37, reach an adder 41 via a delay circuit 40 that provides a binaural time difference, and are sent via an intensifier 43. Applied to the electroacoustic transducer on the right side of the headphones. At this time, due to the action of the two signals applied to both air-acoustic transducers, the headphone listener can recognize the sound image localization outside the head, with a sense of distance, to the front left 4y. Next, input terminals 23 and 24
The signal paths of the two rear signals applied to the two rear signals will be explained.
The flow of these two signals presents the recognition of sound image localization similar to the state in which the speakers 3 and 4 in FIG. 1 are raised. The right rear signal applied from the input terminal 23 reaches the adder 38' via the correction circuit 33a, is mixed with the reflected blue signal which reaches the low-pass filter 33a', and is mixed with the reflected blue signal which reaches the adder 38' via the adders 42', 41 and the amplifier 43. is applied to the electroacoustic transducer 45 on the right side of the headphones. At the same time, the right rear signal that has passed through the correction circuit 33b is mixed with the reflected blue signal that has passed through the low-pass filter 33b' in an adder 37', and after being given a binaural time difference by a delay circuit 40', an adder 41', It is released via an intensifier 44 to an electroacoustic transducer 46 on the left side of the headphones. At this time, the headphone listener uses the action of these two signals applied to both electroacoustic transducers to localize the sound image outside the head with a sense of distance.
Recognize in 5o. Next, the left rear signal applied from the input terminal 24 reaches the adder 35' via the correction circuit 34a, and is mixed with the reflected sound signal via the low-pass filter 44a'. The signal is applied to the electroacoustic transducer on the left side of the headphone through the intermediate device 44, while simultaneously transmitting the signal through the correction circuit 34b and the low-pass filter 3.
4b' is mixed with the reflected sound signal by the adder 36', and is delayed by the delay circuit 39' by the binaural time difference.
2', 41 and the intensifier 43 to the electroacoustic transducer on the right side of the headphones. At this time, the headphone listener can recognize the sound image localization with a sense of distance to the rear left 45o due to the action of these two signals. I can do it. The above describes the flow of signals from the four input terminals to which 4CH signals are applied to the electroacoustic transducers of the listener's headphones in this embodiment. The effect of providing a sense of direction and distance in localization is due to the reflected blue signal created by the delay circuit and low-pass filter, the frequency correction circuit that provides directional information, and the movement of the delay circuit that provides the binaural time difference. Furthermore, in the embodiment shown in FIG. 4, since the times of the delay circuits 39, 40, 39', and 40' can be set independently, the direction of sound image localization for each CH can be arbitrarily determined. , and further variable resistance attenuator 2
By adjusting 9 and 29' to change the reflected sound signal and the bell, the distance of the sound image can be changed from inside the head to outside the head, or vice versa. In particular, the frequency characteristics of the front sound and the rear sound of direct sound and indirect sound in reproduction by a 4-channel speaker are different.

This is because the listener's ears are facing forward, and in order to achieve the same listening condition with headphones as with this 4-channel speaker reproduction, it is necessary to combine the front cost and rear sound of the direct sound signal and indirect sound signal. need to be processed separately. In the present invention, since signals are processed through front and rear phase shifters having different characteristics, a low-pass filter, and a frequency characteristic correction circuit, the present invention has the advantage that listening conditions similar to those reproduced by four-channel speakers can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the state of front and rear 2-2 system 4CH speaker listening, Figure 2a is a sound pressure frequency characteristic diagram of the sound from the front speakers at 45o, 1 measured with an artificial head microphone, Figure 2 b is a sound pressure frequency characteristic diagram obtained by measuring the sound from a speaker at 1 skin at 45 degrees rear with a human mouth microphone, and Fig. 3 is a schematic diagram of a conventional 4CH headphone device.
FIG. 4 is a block diagram of a 4CH headphone device according to an embodiment of the present invention. 21, 22, 23, 24...input terminal, 25, 26, 2
5', 26'... Adder, 27, 27'... Delay circuit, 28, 28'... Feedback circuit, 29, 29'
... Variable attenuator, 30, 30' ... Phase shift circuit, 31
a, 31b', 32a', 32b', 33a', 33b
', 34a', 34th...Low pass filter, 35,
36, 37, 38, 35', 36', 37', 38'...
...Adder, 39, 39', 40, 40'...Delay circuit, 41, 42, 41', 42'...Adder, 43, 44...Amplifier, 45 , 46... Electroacoustic transducer. Figure 1 Figure 2 Figure 3 Figure Size Ship

Claims (1)

[Claims] 1. Of the four direct sound signals obtained by reproducing a 4-channel program source, the front two signals are added together, the rear two signals are also added, and these two added signals are sent to a delay circuit each having a feedback circuit. After passing through the , each output signal is divided into two, and one of the two divided output signals has a difference between the frequency-phase amount transition and the phase amount transition of about 4KHz.
4 through phase shifters ranging from 0 degrees to π in the following bands, respectively.
Four interaural sound signals are output through a low-pass filter for the front two signals with a cut-off frequency of about 4 KHz and a low-pass filter for the rear two signals with a cut-off frequency of about 2 KHz.
The two direct sound signals are synthesized with the indirect sound signal via front and rear frequency characteristic correction circuits with different characteristics that approximate the transfer characteristics of a four-channel speaker reproduction system, and are further synthesized with the indirect sound signal to provide a binaural time difference. A 4-channel headphone device characterized in that the signal is synthesized into a 2-channel signal via a delay circuit and is listened to by a 2-channel headphone.