JPS6057798A - Silencer type speaker acoustic box - Google Patents

Abstract

PURPOSE:To improve sound absorbing efficiency by decreasing the cross-sectional area of an acoustic box toward the inside of the acoustic box from a speaker mounting part. CONSTITUTION:A speaker 1 is mounted on a front buffle board 2, the cross-sectional area of the acoustic box is decreased toward a backward direction so as to narrow a sound path 5 and a port 3 and an air flow resistance board 4 are provided to the rear end part. Since the sound path 5 is narrowed toward the backward direction, both ends of wave front touch the inner face at one point in the sound wave irradiated from the back side of the speaker and the wave is restricted for propagation so that the wave front is deformed into a bow. The compressional wave of sound is cancelled together and the sound absorbing effect is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speaker sound box having a sound-dampening structure that improves sound absorption efficiency.

Previously, as a method of absorbing the sound pressure inside a speaker acoustic box, the sound-absorbing effect was achieved by covering the inside of the box with sound-absorbing materials such as glass wool or felt.

The present invention improves sound absorption efficiency by speeding up the sound pressure decay time in the sound box than in the past by using a sound box structured so that the sound pressure radiated from the back of the speaker is guided by the sound pressure self-cancelling action. It is characterized by increasing.

The sound-absorbing effect of conventional sound-absorbing materials is to stop the air vibrations inside the sound box caused by the back of the speaker by using the frictional resistance provided by the sound-absorbing materials. Although the sound absorption effect increases, this results in an increase in the air vibration resistance and the mass of the vibration system inside the acoustic box, which indirectly increases the vibration load on the back of the speaker diaphragm and increases the driving force of the speaker's vibration. That acceleration,
Since it is consumed by the frictional resistance of the sound-absorbing material, it tends to cause a decrease in volume and aging of transient characteristics.In particular, in the sound-absorbing frequency band of the sound-absorbing material, the lower the frequency, the more
Because of its tendency to reduce sound absorption, a large amount of sound absorbing material was required to achieve sufficient sound absorption up to low frequencies. In this case, the sound-absorbing material itself had an adverse effect on the overall balance of sound quality, so there was a stalemate in improving the sound quality. In addition, with existing acoustic boxes, the sound pressure cannot be absorbed once it reaches the inner surface covered with sound absorbing material, so each time the sound is reflected from the inner surface, the number of times the sound absorbing material is passed through the box increases.
Attenuates sound pressure while increasing cargo distance. Correspondingly, the sound pressure decay time is long, and the reaction time occurring on the rear surface of the speaker is also long, leading to deterioration of transient characteristics or deterioration of sound quality due to reverberation.

The present invention speeds up the sound pressure decay time by canceling out the compressional waves of the sound during the transmission process of sound in a certain direction, thereby reducing the amount of sound-absorbing material used significantly compared to the conventional method. Therefore, the sound absorption effect is enhanced without suppressing the sound, and it is desired to raise the limit of improvement in sound quality and reproduce high-fidelity sound with rich volume and high transparency.

Figure 1 is a basic structural diagram of a sound-reducing sound box.The speaker (1) is attached to the front wall plate (2), and the cross-sectional area of the sound box decreases as it goes towards the rear. At the rearmost part, the port (3) and the air flow resistance plate (4) are installed.
will be established.

Figure 2 is a development of Figure 1, in which a number of resistance plates (6) are used to narrow the sound path as it goes backwards.
The area of the resistor plate is increased toward the rear, narrowing the sound path (5) and reaching the port (3).

In FIGS. 1 and 2, as the sound pressure radiated from the rear surface of the speaker is transmitted rearward, the sound pressure carrying area is reduced, and the sound pressure propagates while reducing the amount of sound pressure transmitted. The sound wave transmission body at that time is shown in FIG. The wavefront of the sound waves emitted from the back of the speaker is A~
Represented by E, as you go backwards, the sound path (5)
As the wave becomes narrower, both ends of the wave surface come into contact with the inner surface, which impedes the progress of that part, and as it moves backward, the wave surface deforms into an arched shape as shown in A to E. . The phase bodies of the wavefront at this time are waveforms (1) and (2
). The solid line waveform (1) indicates the phase at the tip of the wavefront, and the wavy line waveform (2) indicates the phase at both ends of the wavefront. As the wave front progresses, it becomes arched, so the waveform,
The angle becomes wider and the phase range becomes wider. The initial phase range, a' to a, becomes wider from e' to e as it goes backward, and the E wavefront overlaps the D wavefront, which is in the opposite phase, and the waveform d
and e' become a body in which they overlap with opposite phases. As a result, the phase d at the tip of the D wavefront cancels the phase e' at both ends of the E wavefront. The sound pressure reaching the port (3) and the sound pressure due to the optimum resonance frequency of the sound box are consumed by the acoustic frictional resistance provided by the air flow resistance plate (4). Fig. 4 shows the same effect, but the wave front is forcibly blocked by a large number of resistance plates (6) compared to the one in Fig. 3, and the sound pressure is left behind between the resistance plates (7). As the wave surface progresses through the sound path (5) while deforming into an arched shape, in addition to waveforms (1) and (2), a part of the wave surface left behind between the resistor plates (7) and a wavy line waveform (3) is shown, and in order to increase the overlap of opposite phases, the silencing effect is made more forced than in the case shown in Fig. 3.

For the above purposes, under conditions where sound pressure transmission is set in a certain direction and the sound pressure transmission carrying area is reduced, the sound pressure transmission speed is partially determined or weakened during the process of sound wave transmission. As a result, the areas of both the compression and compression waves of the sound wave become wider in the direction of propagation, so the areas of the compression and compression waves overlap and cancel each other.

The objects shown in FIGS. 5 and 6 are actual examples manufactured for a 20 cm diameter speaker, and are approximately 1/10 scale drawings. For practicality, this method depends on the case where it is preferable to install the speaker vertically, and the direction of the speaker and port is changed to the front. In terms of the amount of material used, compared to conventional acoustic boxes, the square area of each surface on which sound pressure is applied is structurally smaller, so relatively thinner laminated lauan plywood or the like can be used than in the past, with a thickness of about 12 m/m. The resistance plate is
It only needs to be about 6 m/m thick, and by just using a small amount of reinforcing material (1), it is lighter and less likely to cause ringing than conventional sound boxes. Each joint is joined using a woodworking adhesive. The sound absorbing material (2) may be applied thinly over the entire inner surface or only at key points.

Figure 7 shows the installation method used when a large volume is required, and in particular, the acoustic box of the shape shown in Figure 1 can be stacked on top of each other in multiple stages, and can be used for commercial purposes. Since it is light in weight, it is convenient to transport and move. Alternatively, it is easy to manufacture the sub-units as an integral structure in the shape shown in FIG. 7, and the manufacturing cost per piece is limited.

[Brief explanation of drawings]

Figures 1 and 2 are basic structural diagrams, and (A) is
A side sectional view, (B) a partial sectional view of a front view, and (C) a rear view. FIGS. 3 and 4 are explanatory diagrams showing the working body. 5, 6, and 7 are diagrams showing embodiments. Patent applicant Yuji Kamijo

Claims (2)

[Claims] (1) A sound-reducing speaker sound box in which the cross-sectional area of the sound box is reduced from the speaker mounting part as it progresses inside the sound box, and the opening area leading to the port is minimized. (2) In a structure that reduces the cross-sectional area of the acoustic box, a large number of resistive plates are installed inside the acoustic box, and the area of the resistive plates increases from the speaker to the port, reducing the sound pressure carrying area. Silent speaker sound box with minimal opening area.