WO2003013189A1 - Acoustic reproduction apparatus - Google Patents

Abstract

An acoustic reproduction apparatus controls phase of sound waves generated from a right and a left loudspeaker, thereby generating preferable acoustics. At least two power amplifiers amplify an output signal of a signal source. At least two loudspeakers reproduce sound by the output signals from the two power amplifiers. An n-order phase shifter is coupled to at least one of the two power amplifiers and changes the phase of the output signal of the signal source.

Description

Technical field

 The present invention provides, for example, a sound reproduction device used as a sound muffler that reproduces sound with good sound quality and satisfactorily reduces noise in a vehicle interior.

Related to the device.

 Field background technology

 Conventionally, for example, an on-vehicle sound reproducing device as shown in FIG. 12 is known.

 In FIG. 12, a signal source 101 for supplying music signals and the like, a first power amplifier 103, and a second power amplifier 104 are connected to a signal source 101, respectively. The output of the first power amplifier 103 is connected to a speed force 5 attached to the left door of the vehicle 107. A speaker 106 attached to the right door of the vehicle 107 is connected to the output of the second power amplifier 104. In this way, the user can enjoy playing music and the like in the cabin.

 However, in such a conventional configuration, the acoustic space is narrow and the listener is located at a position deviated from the center position of the two opposing speech forces 105 and 106. For this reason, the sound pressure and phase characteristics of the sound reaching the listener's ear vary greatly as the frequency increases.

Figures 13 and 14 show the data measured by the dummy head in the actual vehicle interior. Fig. 13 and Fig. 14 show the phase difference and sound pressure difference of the sounds entering the left and right ears, respectively.

 In this example of the vehicle, the sounds entering the left and right ears of the listener near 250 Hz are in opposite phases as shown in FIG.

 The reason why such a phenomenon occurs is as follows.

 The wavelength of the 250 Hz signal is 1.36 m. This is almost the same as the distance from the left door to the right door in the cabin. In addition, the listener sits off the center of the two speeds 105 and 106. Thus, due to the difference in the distance between the listener's position and the two speeds 105 and 106, the right and left speakers transmit sounds whose phases differ by approximately 180 degrees to the listener. . Thus, the phenomenon described above occurs.

 Therefore, from the viewpoint of sound quality, the sense of opposite phase of the sound is strongly detected. That is, at the position of the recipient, relative to the left and right ears of the listener, the phases of the sounds entering the left and right ears are reversed, as shown in Fig. 14. The sound pressure level also fluctuates greatly. Thus, the balance between the sounds entering the left and right ears at the position of the religious person is poor.

 Also, when a sound-muffling system is configured with the same device as described above, a noise having a phase opposite to that of noise for canceling noise is generated at the listener's position. At this time, if the sounds having opposite phases reach the right and left ears of the listener as described above, the sound deadening performance cannot be obtained.

 As described above, in the conventional device, an unnatural reproduction sound may be obtained depending on the distance between the left and right speakers and the position of the listener. Disclosure of the invention

An object of the present invention is to provide a sound reproducing device having good sound quality. At least two power amplifiers amplify the output signal of the source. At least two speakers reproduce sound using the output power of the two power amplifiers. An nth-order phase shifter is coupled to at least one of the two power amplifiers to change the phase of the output signal of the signal source.

Thus, the sound reproducing device of the present invention controls the phases of the sound waves generated from the left and right speakers, and reproduces good sound. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a system diagram for describing Embodiment 1 of the sound reproduction device of the present invention.

 FIG. 2 is a circuit diagram for explaining the phase shifter according to the first embodiment. FIG. 3 illustrates characteristics of the phase shifter according to the first embodiment.

 FIG. 4 illustrates the phase characteristics of the system according to the first embodiment.

 FIG. 5 illustrates the sound pressure characteristics of the system according to the first embodiment.

 FIG. 6 is a system diagram for describing Embodiment 2 of the sound reproduction device of the present invention.

 FIGS. 7A and 7B are circuit diagrams for explaining the phase shifter according to the second embodiment.

 FIG. 8 illustrates the phase characteristics of the phase shifter according to the second embodiment.

 FIG. 9 is a characteristic diagram for explaining a relative phase difference of the phase shifter according to the second embodiment.

 FIG. 10 is a system diagram for describing Embodiment 3 of the sound reproduction device of the present invention.

FIG. 11 is a system diagram for describing Embodiment 4 of the sound reproducing device of the present invention. FIG. 12 is a diagram for explaining a conventional sound reproducing device. Figure 13 illustrates the phase characteristics of the conventional system,

 FIG. 14 illustrates the sound pressure characteristics of a conventional system.

 Hereinafter, embodiments of the present invention will be described with reference to FIG. 1 to FIG.

(Embodiment 1)

 FIG. 1 is a system diagram for explaining Embodiment 1 of the sound reproducing device of the present invention.

 FIG. 2 is a circuit diagram showing a phase shifter according to the present embodiment.

 FIG. 3 is a characteristic diagram showing frequency vs. gain and phase characteristics of the phase shifter according to the present embodiment.

 In FIG. 1, a signal source 1 for supplying a music signal or the like is coupled to a first power amplifier 3 through an n-order phase shifter 2. Further, the signal source 1 is coupled to the second power amplifier 4. The speed 5 mounted on the door of the vehicle 7 is driven by the first power amplifier 3. Another speed force 6 attached to the door of the vehicle 7 is driven by the second power amplifier 4.

 In other words, here, the signal source 1 and the two-channel power amplifier and the speeds 5 and 6 form a sound reproduction system.

Here, the n-order phase shifter is configured by combining, for example, n phase delay circuits of approximately 180 degrees. Where n is an integer. Therefore, the first-order phase shifter is composed of, for example, a delay circuit that keeps the gain constant and delays the signal phase by approximately 180 degrees as the frequency increases. The phase shifter 2 used in the present embodiment is a fourth-order phase shifter. In other words, it is a 4 x approximately 180 degree delay circuit. As shown in the circuit diagram of FIG. 2, these are the capacitors 8, 11, 14, 17, the resistors 9, 10, 10, 12, 13, 15, 15, 16, 18, 19, and 2 It consists of two operational amplifiers 20 and 21. In the frequency vs. gain and phase characteristics of the phase shifter 2, the gain is constant as shown in FIG. 3, and the phase is delayed as the frequency increases.

 Here, in the phase shifter of FIG. 2, two second-order phase shifters are connected in series. Here, the gain is constant and the phase changes by 360 degrees for the frequency of the signal passing through one second-order phase shifter. Here, the frequency ranges of the two second-order phase shifters are selected so that the curve of the phase change with respect to the frequency is continuous.

 In the conventional system, as shown in Fig. 14, at the listening point, the phase of the sound reaching the left and right ears of the listener is inverted around 260 Hz. In this system, the above-described fourth-order phase shifter 2 is provided before the first power amplifier 3. As a result, as shown in FIGS. 4 and 5, the phase change width up to around 400 Hz is improved to within ± 90 °. Here, the sound pressure difference between the sounds coming from the left and right of the listener is also improved to within ± 10 dB.

 In the above example, a fourth-order phase shifter is used. Not limited to the fourth-order phase shifter, an n-order phase shifter may be used. Even in the nth-order phase shifter, the sounds reaching the left and right ears of the listener are near frequencies that are out of phase with each other, and the phase of one sound is further shifted by approximately 180 degrees. Its characteristic force S is set. At this time, similarly to the above, the phase difference and sound pressure difference of the sound reaching the right and left ears of the listener from the left and right can be improved.

In general, the sound level reaching the left and right ears of the listener depends on the width of the cabin. The frequency at which the phases are reversed changes. Therefore, the frequency band of the phase shifter may be adjusted according to the width of the cabin.

 With such a configuration, a sound of good sound quality is reproduced in the vehicle cabin, which is less affected by the sound pressure difference between the opposite phase sound and the sound coming from the left and right.

(Embodiment 2)

 FIG. 6 is a system diagram for explaining Embodiment 2 of the sound reproducing device of the present invention.

 FIG. 7 is a circuit diagram showing a phase shifter according to the present embodiment. 6 and 7, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described.

 FIG. 8 is a characteristic diagram showing the phase characteristics of the two phase shifters in FIG. FIG. 9 is a characteristic diagram showing a relative phase of two phase shifter outputs when the phase shifter shown in FIG. 8 is configured.

 As shown in FIG. 6, an n-order phase shifter 22 is provided before the first power amplifier 3. An n-order phase shifter 22 is provided before the second power amplifier 4. This circuit configuration is constructed by connecting the basic configuration of the secondary phase shifter shown in Figs. As shown by characteristic curves A and B in FIG. 8, the two phase shifters 2 and 22 have different phase rotation center frequencies, respectively.

 By doing so, as shown in FIG. 9, the relative phase difference between the sounds emitted from the two channels can be 180 degrees at a certain frequency. In other words, the sounds coming out of the two channels will be out of phase with each other at their frequency.

With this configuration, the sounds from the two channels are Reverse phase to become part of the frequency can be set in the vicinity of 2 5 0 H _Z. On the other hand, in the phase characteristic of the conventional system shown in FIG. 13, the frequency portion having the opposite phase is around 250 Hz.

 Therefore, conventionally, the relative phase of the sound waves radiated from the left and right loudspeakers is further opposite in a frequency portion where the relative phases are opposite to each other. As a result, phase correction can be realized.

 With such a configuration, very good sound quality can be obtained as in the first embodiment of the present invention. (Embodiment 3)

 FIG. 10 is a system diagram for describing Embodiment 3 of the sound reproducing device of the present invention. The same components as those in Fig. 1 are assigned the same numbers, detailed description is omitted, and only different components are described.

 In this sound reproducing device, the microphone 24 detects noise. The filter 23 is adjusted so that the output signal of the microphone 24 has the opposite phase to the noise source and is output. The output signal of the filter 23 is distributed to two channels.

 The two power amplifiers 3 and 4 amplify the distributed two-channel signal. The loudspeakers 5 and 6 generate noise reduction to reduce noise by the output power of the power amplifiers 3 and 4.

 Here, the speakers 5 and 6 are attached to left and right doors of the vehicle 7. As described above, this sound reproducing device has a sound deadening function.

 Here, an n-order phase shifter 2 is provided in a stage preceding the first power amplifier 3.

The sound reproducing device according to the present embodiment has a small phase difference between the left and right ears of the listener. Reaches the sound-absorbing sound and shows an excellent sound-absorbing effect. This is based on the same operating principle as that of the sound reproducing device of the first embodiment transmitting sound with a small phase difference to the left and right ears of the listener.

 Further, the sound reproducing device having the sound deadening function may be used in combination with the sound reproducing device described in Embodiment 1 as shown in FIG. In this case, there is provided a sound reproducing apparatus that silences noise while transmitting sound with a small phase difference to the left and right ears of the listener.

(Embodiment 4)

 FIG. 11 is a system diagram for explaining Embodiment 4 of the sound reproducing device of the present invention.

 The same components as those in FIG. 10 are denoted by the same reference numerals, detailed description is omitted, and only different components are described.

 An n-order phase shifter 2 is provided before the first power amplifier 3, and an n-order phase shifter 22 is provided before the second power amplifier 4. Here, the phase rotation center frequencies of the phase shifters 2 and 22 are set to different frequencies.

 With such a configuration, the sound reproducing device according to the present embodiment can obtain an excellent sound deadening effect by the arrival of the sound deadening sound having a small phase difference. This is based on the same operating principle as that of the sound reproducing device according to the second embodiment transmitting sound with a small phase difference to the left and right ears of the listener.

Further, the sound reproducing device having the sound deadening function may be used in combination with the sound reproducing device described in the second embodiment as shown in FIG. In this case, there is provided a sound reproducing apparatus that silences noise while transmitting sound with a small phase difference to the left and right ears of the listener. Industrial applicability

 As described above, in the present invention, at least a two-channel power amplifier is used. It amplifies the output voltage of a signal source that supplies music and the like. At least two loudspeakers reproduce sound using the output power of the two-channel power amplifier. Here, an n-order phase shifter is coupled to at least one of the two-channel power amplifiers. This makes it possible to obtain an extremely good sound reproducing device in the vehicle interior, which is less affected by the sound pressure difference between the opposite phase sound and the sound coming from the left and right.

 In addition, according to the same operation principle, the present invention provides a sound reproducing device having excellent sound deadening performance that operates well in a vehicle interior.

Claims

The scope of the claims 1. At least two power amplifiers for amplifying the output signal of the signal source, and at least two speeds for reproducing sound by the output signals of the at least two power amplifiers;  An nth-order phase shifter (where n is an integer) coupled to at least one of the at least two power amplifiers for changing a phase of an output signal of the signal source; Including Sound reproduction device. 2. Each of the at least two power amplifiers has an nth-order phase shifter (where n is an integer) having a different phase rotation center frequency and changing the phase of the output signal of the signal source. Combined The sound reproducing device according to claim 1. 3. The n-order phase shifter is a fourth-order phase shifter The sound reproduction device according to claim 1. 4. The n-order phase shifter is a fourth-order phase shifter The sound reproduction device according to claim 2. 5. The signal source includes a microphone for detecting noise, A filter to which an output signal of the microphone-mouth phone is input and that outputs a signal having a phase opposite to that of the noise, The at least two loudspeakers generate a noise reduction to reduce the noise according to an output signal of the filter. The sound reproducing device according to claim 1. 6.  A microphone for detecting noise,  A filter to which an output signal of the microphone mouth phone is input and that outputs a signal having a phase opposite to that of the noise; Including  An output signal of the filter is distributed to at least two channels, and is input to the at least two power amplifiers. The at least two speakers reduce the sound supplied from the signal source and the noise. Let the sound destruction and generate The sound reproducing device according to claim 1. 7. An nth-order phase shifter (where n is an integer) that changes the phase of the output signal of the signal source and has a different phase rotation center frequency is coupled to each of the two power amplifiers. The sound reproducing device according to claim 5. 8. Each of the two power amplifiers is coupled to an nth-order phase shifter having a different phase rotation center frequency and changing the phase of the output signal of the signal source. The sound reproducing device according to claim 6. 9. The sound reproducing device according to claim 7, wherein the n-order phase shifter is a fourth-order phase shifter.