JPS6031346Y2 - Braking device in headphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a braking device for a headphone that makes the quality of the product uniform and also contributes to reducing peak dips in frequency characteristics.

Conventionally, a damping material made of polyurethane foam has been used on the back side of an electroacoustic conversion unit in headphones for the purpose of adding acoustic resistance.

Polyurethane foam is designed to exhibit optimal acoustic resistance properties based on the number of cells expressed by the so-called expansion ratio.

However, conventional sound damping materials for headphones made of polyurethane foam have the following drawbacks because they are simply processed by slicing, punching, or other machining operations on a foamed raw material to obtain desired dimensions and shapes.

That is, during the foaming process during the production of polyurethane foam, as shown in Figure 1, a membrane-like body called a mirror is stretched between the skeletal structures C on the surface of the cells a, and the density of the generated mirrors is There is considerable variation depending on the temperature conditions during generation.

In addition to variations between the lofts of the original fabric, local variations in the mirror generation density are observed even within the same fabric.

Therefore, even if the foaming ratio is determined to obtain the optimum acoustic resistance characteristics at the time of design, the mirror density may be large due to variations in the density of mirror generation during mass production, that is, variations in the density of the film-like material on the surface of each bubble. If there is, the acoustic resistance increases because the area that does not have air permeability relative to the bubbles that function as acoustic resistance increases.

On the other hand, if the mirror density is small, the area that does not have air permeability to air bubbles will be relatively reduced, so the acoustic resistance will be reduced.

As a result, variations in sound pressure frequency characteristics will ultimately appear during mass production.

This results in variations in the product characteristics of each finished headphone product, and even differences in characteristics between the L channel and R channel of the same headphone, which poses a problem in mass producing headphones of uniform quality. It had become.

This invention was devised in view of the above-mentioned problems, and its purpose is to eliminate the product characteristics or unbalance between channels in this type of headphone, and to achieve uniformity of the product.

In order to achieve the above-mentioned object, this invention is patented, characterized in that a cellular polymer obtained by destroying cell membranes and forming a network is used as the material of the damping material.

A preferred embodiment of this invention will be described below in detail with reference to the accompanying drawings.

Cellular polymers, as is well known, consist of a large number of cells, and these cells are generally made up of intersecting cell wall elements.
It consists of a dimensional skeletal structure and interconnected fibers that are attached to the skeletal structure and have membranes or openings that define adjacent cells.

This membrane can then be broken to allow communication between cells in the cellular material, or it can be left unbroken.

As described above, this variation in film formation causes non-uniformity in the properties of the final product.

Therefore, in this invention, as a material for the damping material, as shown in Fig. 2, there is no membranous body between the skeletal structures C and skeletal structures C constituting cell a, that is, the cell membrane is destroyed to form a reticulated material. Polymerized cellular polymers (e.g. polyurethane foam, etc.) are used.

FIG. 3 is a partially cutaway side view showing an example of a headphone using a damping material made of a cellular polymer having such a cellular structure.

The figure shows only one of the left and right horns that make up the headphone. 1 is the headband, 2 is Herad leather, and 3 is the headband.
is an arm, and a horn main body 4 is attached to this arm 3 via a universal joint 5 so as to be freely bendable.

An electroacoustic transducer 7 is fixed in a thin disk-shaped casing 6 formed by forming a circular opening on the ear-high side of the horn body 4, and an inner periphery of the casing 6 that faces the outer periphery of the transducer 7. A damping material 8 made of felt is provided on the surface, and a damping material 9 made of polyurethane foam is provided on the inner surface of the casing 6 facing the back surface of the converter 7, and an ear pad 10 is fixed to the opening of the casing 6. It is composed of

The electroacoustic transducer 7 is of the fully driven type in this example, and the signal supply to this transducer 7 is carried out by a cord 11.

The cells of the polyurethane foam forming the damping material 9 have completely destroyed cell membranes, as shown in FIG.

Note that various known methods can be used to destroy the cell membrane in this way. For example, most of the cellular material will not be damaged, but at least the cell membrane will be destroyed sufficiently to the extent that it will be volatilized by the high heat. A so-called explosive method, in which high temperature and high pressure conditions are applied to the cellular material for a short period of time, can be used.

According to the above configuration, since polyurethane foam with completely destroyed cell membranes is used as the material for the damping material 9, the acoustic noise caused by the variation in the density of mirror generation between lofts or within the same raw material is avoided, as in the past. Variations in resistance are eliminated, the characteristics of the damping material 9 are made uniform, and a headphone having a uniform sound pressure frequency can be provided even during mass production.

Figure 4 is a graph showing the sound pressure frequency characteristics of the headphone according to this invention in comparison with that of a headphone with a conventional structure.As is clear from this graph, when compared with the conventional characteristic curve It can be seen that the characteristic curve (■) of the headphone is relatively flat with little peak depth.

That is, by using polyurethane foam with completely destroyed cell membranes as the material for the damping material 9, it is possible to reduce the peak dip in the sound pressure frequency characteristic curve without lowering the sound pressure level.

As is clear from the above description, the present invention is a headphone in which a damping material for adding acoustic resistance is arranged on the back side of an electroacoustic transducer unit. Since it is made of cellular polymer, it is possible to maintain uniform quality of this type of headphone even during mass production, eliminate imbalance between the left and right channels of each headphone, and further improve sound pressure frequency characteristics. It has various features such as contributing to the

[Brief explanation of the drawing]

Fig. 1 is a schematic structural diagram showing the state of cells in a conventional damping material, Fig. 2 is a schematic structural diagram showing the state of cells in a damping material according to the present invention, and Fig. 3 is a schematic structural diagram showing the state of cells in a damping material according to the present invention. FIG. 4, a partially cutaway side view, is a graph comparing the headphone according to the present invention with a conventional headphone in terms of sound pressure frequency characteristics. 7... Electro-acoustic transducer unit, 9...
- Braking material, a... Cell.

Claims (2)

[Scope of utility model registration request] (1) In a headphone in which a damping material for adding acoustic resistance is arranged on the back side of an electroacoustic transducer unit,
A braking device for headphones, characterized in that the braking material is formed of a cellular polymer obtained by destroying cell membranes and forming a network; (2) The braking device for a headphone according to claim 1, wherein the cellular polymer is a visible polyurethane foam.