JPH04369997A - Speaker system - Google Patents

Abstract

PURPOSE:To obtain a speaker system which can prevent the standing wave to occur in an acoustic horn. CONSTITUTION:In a speaker system to store a speaker unit 1 to radiate the sound to the external part in a cabinet 2, arrange an acoustic horn 4 at the front surface of the speaker unit 1 and guide the sound radiated from the speaker unit 1 up to a buffle surface 3, a resonance tube 7 is fitted at the acoustic horn 4, the standing wave to occur in the acoustic horn 4 with the resonance tube 7 is adsorbed, and thus, the peak dip of the frequency-sound pressure characteristic is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a speaker system for preventing standing waves generated within an acoustic horn.

0002

2. Description of the Related Art FIG. 7 is a sectional view showing the structure of a conventional speaker system. In the figure, 1 is a speaker unit that radiates sound to the outside, 2 is a cabinet that houses the speaker unit 1, etc., 3 is a baffle surface of the speaker system, and 4 is a baffle surface 3 that radiates sound from the speaker unit 1. 5 is an opening of the acoustic horn 4, and 6 is a throat of the acoustic horn 4.

Next, the structure and function of each part will be explained. In the speaker system shown in FIG. 7, a speaker unit 1 that radiates sound to the outside is housed in a cabinet 2. An acoustic horn 4 is installed in front of the speaker unit 1, and guides the sound radiated from the speaker unit 1 to the baffle surface 3 of the speaker system. The acoustic horn 4 is connected from the throat 6 to the opening 5.
It has a structure in which the cross-sectional area gradually increases as it advances.

0004

A conventional speaker system is constructed as described above. When the above-mentioned speaker system is built into equipment such as a TV, the horn length LH of the acoustic horn 4 cannot be made long enough, so a sudden change in acoustic impedance occurs at the opening 5 of the acoustic horn 4, and the opening 5 A part of the sound guided up to this point becomes a reflected wave and returns to the inside of the acoustic horn 4.

[0005] Since the reflected waves described above become standing waves within the acoustic horn 4, a resonance phenomenon occurs within the acoustic horn 4 at a frequency fH determined by the horn length LH, horn shape, etc. Therefore, the frequency-sound pressure characteristics of the conventional speaker system end up having many peaks and dips, as shown by A in FIG.

[0006] As a method for preventing standing waves generated within an acoustic horn, there is a method of absorbing standing waves by composing the acoustic horn with a sound absorbing material, as shown in Japanese Patent Laid-Open No. 63-313998. However, this method had the problem that not only standing waves but also middle and high frequency sounds were absorbed more than necessary.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a speaker system that can prevent standing waves generated within an acoustic horn.

[0008]

[Means for Solving the Problems] A speaker system according to the present invention has a resonance tube attached to an acoustic horn.

Further, in the speaker system according to the present invention, the resonance tube attached to the acoustic horn has a resonance frequency equal to the resonance frequency of the acoustic horn, and further, the attachment position thereof is near the throat of the acoustic horn. .

0010

[Operation] The speaker system of the present invention uses a resonance tube attached to the acoustic horn to absorb standing waves generated within the acoustic horn, thereby reducing peaks and dips in the frequency-sound pressure characteristics.

[0011]

【Example】

Embodiment 1 FIG. 1 is a sectional view showing the structure of a speaker system according to an embodiment of the present invention. In the figure, 7 is an acoustic horn 4
This is a resonant tube that absorbs the standing waves generated inside the tube. The other parts are the same as those of the conventional example, so the explanation will be omitted.

Next, sound absorption by a resonance tube will be explained with reference to FIGS. 2 and 3. FIG. 2 shows the state of resonance in a resonant tube of length LR by a particle velocity distribution. As shown in Figure 2, a resonance tube is a tube with one end closed and the other open, and f
Rn= (2n-1)c/4L...(a) However, fRn:
Resonance frequency [Hz] c: Speed of sound [m/s] L: Effective length of resonance tube [m] n: Resonance phenomenon occurs at the frequency of the resonance order (n=1, 2, 3,...). The effective length L is determined by the conditions of the resonance tube. For example, if the resonance tube is cylindrical and has a flange at the open end as shown in Figure 1, L=LR +8a/3π...(b) where LR: resonance tube Length [m] a: Radius of resonance tube [m].

FIG. 3 is a diagram showing the sound absorption characteristics of the resonance tube shown in FIG. 2. When air enters and exits the resonance tube, the acoustic resistance ra of the resonance tube converts sound energy into thermal energy, causing sound absorption. At frequencies near the resonance frequency, air enters and exits the resonance tube actively, so the sound absorption coefficient of the resonance tube has a peak at the resonance frequency, and the first resonance frequency fR1 (in equation a, when n = 1 ) is the maximum. Furthermore, if the acoustic resistance ra of the resonance tube is increased by, for example, inserting a sound absorbing material into the resonance tube, the sound absorption coefficient at the peak becomes smaller, but the frequency band in which sound is absorbed becomes wider.

Therefore, in the present invention, a resonance tube 7 is attached to the acoustic horn 4, and the first-order resonance frequency fR of this resonance tube 7 is
1 is adjusted to be equal to the resonant frequency fH of the acoustic horn 4 (see formulas a and b), and standing waves generated within the acoustic horn 4 are absorbed.

On the other hand, the particle velocity distribution of the standing wave generated within the acoustic horn 4 has an antinode location and a nodal location. If the resonant tube 7 is attached to the antinode location, standing waves can be efficiently absorbed, but if the resonance tube 7 is attached to the node location, it becomes difficult to absorb the standing wave. Further, as the ratio of the cross-sectional area of the open end of the resonance tube 7 to the cross-sectional area of the acoustic horn 4 at the portion where the resonance tube 7 is attached increases, the absorption of standing waves becomes easier.

Therefore, in the present invention, the throat 6 of the acoustic horn 4
Resonant tube 7 is placed near the location where the particle velocity distribution of the standing wave has an antinode.
is installed.

Since the speaker system according to the present invention is constructed as described above, only the standing waves generated within the acoustic horn 4 are effectively absorbed by the resonance tube 7, and the frequency-sound pressure characteristics of the speaker system are as shown in the figure. Like B in 4, the peak and dip are small.

Embodiment 2 In the above embodiment 1, nothing is contained in the resonance tube 7, but
In order to adjust the sound absorption power of the resonance tube, the resonance tube 7 is
A sound absorbing material 8 may be placed inside. (See Figure 3 for the effect of putting sound absorbing material inside the resonance tube.)

As can be seen from FIG. 2, when the resonance phenomenon is totaled, the particle velocity distribution inside the resonance tube is maximum near the open end, so it is better to insert the sound absorbing material near the open end of the resonance tube to increase the sound absorption power of the resonance tube. can be adjusted effectively.

Embodiment 3 In Embodiment 1, the resonance frequencies of the two resonance tubes are adjusted to the same value, but as shown in FIG. It may be adjusted to the value of .

For example, the first resonance frequency fRA1 of 7A of the resonance tubes is adjusted to be equal to the first resonance frequency fH1 of the acoustic horn 4, and the first resonance frequency fRA1 of the resonance tube 7B is adjusted to be equal to the first resonance frequency fH1 of the acoustic horn 4.
If the next resonant frequency fRB1 is adjusted to be equal to the second resonant frequency fH2 of the acoustic horn 4, the standing waves generated within the acoustic horn 4 can be absorbed more effectively.

Embodiment 4 In the first embodiment described above, two resonance tubes are attached to the acoustic horn 4, but the number of resonance tubes may be one or two or more.

[0023]

As described above, according to the present invention, by absorbing standing waves generated within the acoustic horn using a resonance tube attached to the acoustic horn, the peak of the frequency-sound pressure characteristic can be reduced.・The dip has been reduced, so
This has the effect of making it possible to obtain flat characteristics over a wide frequency range.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a speaker system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the state of resonance in a resonant tube having a length LR by a particle velocity distribution.

FIG. 3 is a sound absorption characteristic diagram of the resonance tube shown in FIG. 2;

FIG. 4 is a frequency-sound pressure characteristic diagram of the speaker system of the present invention and a conventional example.

FIG. 5 is a sectional view showing the structure of a speaker system according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a speaker system according to a third embodiment of the present invention.

FIG. 7 is a sectional view showing the structure of a conventional speaker system.

[Explanation of symbols]

1 Speaker unit 2 Cabinet 3 Baffle surface 4 Acoustic horn 5. Acoustic horn opening 6. Acoustic horn throat 7 Resonance tube

Claims (2)

[Claims] 1. A speaker system in which a speaker unit that radiates sound to the outside is housed in a cabinet, and an acoustic horn is installed in front of the speaker unit to guide the sound radiated from the speaker unit to a baffle surface, A speaker system characterized in that a resonance tube is attached to the acoustic horn. 2. The speaker system according to claim 1, wherein the resonant tube attached to the acoustic horn has a resonant frequency equal to the resonant frequency of the acoustic horn.