JPH04207699A - Pressure vibration detecting element - Google Patents

Abstract

PURPOSE:To improve the above element in such a manner that even extremely low frequencies can be measured by utilizing a condenser microphone by closing the air leak path of a cylindrical body exclusive of its aperture. CONSTITUTION:An adhesive layer 13 adheres a circuit board 3 to the bottom wall surface on the inner side of a case 2 to eliminate the spacing 10 formed between the circuit board 3 and the bottom wall surface on the inner side of the case 2, thereby preventing the flow of the air in and out of the case 2 through the hole 2a of the case 2. The holes, etc., for mounting parts must not be bored in the part of the hole 2a position of the case 2 of the circuit board 3 in such a case. The frequency characteristics in the low frequency region of the condenser microphone are improved down to about 0.1Hz as the counter resonance is eliminated. The frequency characteristics of the low frequency region are easily and greatly improved by the simple constitution in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure vibration detection element such as a condenser microphone or a ceramic microphone.

[Prior Art] The structure of a conventional pressure vibration detection element will be explained using a condenser microphone as an example. That is, the cross-sectional structure of a condenser microphone (+) is shown in FIGS. Since it is ICEM-EM-1211 manufactured by Primo, a detailed explanation will be omitted and a brief explanation will be provided.

(2) is a case with a hole (2a) for taking out lead wires at the bottom, (3) is a circuit board to which a FET (FET) run transistor (4) is attached, and the circuit board (3) is connected to the case (2). A lead wire (not shown) is led out through the hole (2a). (5) is a cylindrical spacing/supporting member with openings at both upper and lower ends, and a plurality of ring-shaped insulating spacers (7 ), the entire peripheral edge of the electret film (6a) forming the pressure receiving surface and its counter electrode (6b) is sandwiched. Therefore, as shown in Fig. 5, the condenser microphone (1) has small gaps (10) formed here and there near the bent end portion (2b) of the case (2).
The air trapped in the space formed inside the condenser microphone (1) leaks through the capacitor microphone (1) through the capacitor microphone (1), and due to pressure fluctuations occurring outside, the electret film (6a) bends and the counter electrode (6b) It changes the capacitance formed between the two and converts pressure fluctuations into an air signal. Also, as shown in Figure 6, each member (2) (3) is placed on the bottom of the condenser microphone (1).
), (s), and when external pressure fluctuations occur, the air is removed through the hole (2a) of the case (2).
The air in the space formed inside the condenser microphone (1) circulates. Note that one lead terminal (4a) of the F E Th transistor (4) is always electrically connected to the counter electrode (6b) of the electret film (6a).

[Problem to be solved by the invention] However, since commercially available microphones, including this type of condenser microphone, were developed for acoustic use, the lower frequencies are audible to the human ear.
Frequency characteristics have only been measured up to about Hz, and there is currently no guarantee in the catalog or as a product. This was not possible due to its performance and structure. Therefore, I measured the frequency characteristics of the above-mentioned condenser microphone (+), which are not listed in the catalog values (in fact, they have not been measured), using a self-made device, and the results are shown in Figure 7. Like IHz~1. ,, anti-resonance characteristic (characteristic is 7
It has been found that the sensor does not have the characteristics as a measurement sensor in the low frequency range, and the source of such frequency characteristics is about 0.1 to IOHz. It was experimentally proven that physical phenomena such as the movement of humans, which have slow motion characteristics, cannot be detected using pressure fluctuations.

[Means for Solving the Invention] ゛Therefore, I developed a completely new and improved technology that uses a low-cost, commercially available audio microphone, especially a condenser microphone, to be able to measure very low frequencies. We propose a microphone, that is, a pressure vibration detection element.The structure is such that a pressure vibration detection means is arranged so as to close an opening at one end of a cylindrical body, and the cylindrical body is closed to prevent air leakage from other than the opening. to block the tract.

[Function] 0.1 Hz, I
Significantly improves low frequency characteristics such as Hz.

[First embodiment] The configuration will be explained based on FIG. 1, but the explanation will be omitted for parts that are the same or equivalent to those explained in FIGS. 4 to 6, and only the different parts will be explained. Give an explanation.

In Figure 1, (13) is an adhesive layer, which is attached to the circuit board (3).
is glued to the inside bottom wall of the case (2).
The gap (10) formed between the circuit board (3) shown in the figure and the bottom wall inside the case (2) is eliminated, and the case (2) is inserted through the hole (2a) of the case (2). ) Prevents the circulation of air inside and outside. However, in this case, it goes without saying that the hole (
2a) There shall be no holes or the like for mounting parts in the part at position 2a).

FIG. 2 shows that by adopting the above configuration, the frequency characteristics of the condenser microphone (1) in the low frequency range are improved to around 0.1 Hz by eliminating anti-resonance. 7 [Second Embodiment] The configuration of this embodiment will be explained based on FIG.
Descriptions of parts that are the same or equivalent to those explained in FIGS. 5 and 6 will be omitted, and only different parts will be described.

First, in Fig. 3, the difference from Fig. 1 is that in Fig. 3, the adhesive layer (13) in Fig. 1 is not used, and the case (2) is
) is sealed from the outside using a sealant (14) to prevent air from flowing inside and outside the case (2).

That is, the sealant (14) closes the lead wire extraction hole (2a) of the case (2) from the outside, and the case (
2) Prevents circulation of air inside and outside. Thereby,
A frequency characteristic similar to that of the above embodiment is obtained as shown in FIG.

Although the above embodiment describes an example in which a condenser microphone is used as a pressure vibration detection element, it goes without saying that the present invention is not limited to this, and any device having a similar function and structure may be used. That's true.

[Effects of the Invention] As described above, the present invention provides a pressure vibration detection element in which a pressure vibration detection means is arranged so as to close an opening at one end of a cylinder. Since the pressure vibration detection element is characterized in that the air leakage path is closed, it is possible to easily improve the frequency characteristics in the low frequency region significantly with a simple configuration. In particular, it is possible to greatly improve the frequency characteristics in the low frequency range of conventional condenser microphones without any modification at all, and it is possible to obtain inexpensive elements without making them expensive. can.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram of essential parts of a condenser microphone according to a first embodiment of the present invention, and FIG. 2 is a frequency characteristic diagram of the condenser microphone shown in the first and second embodiments. FIG. 4 is a cross-sectional view of the main part of the condenser microphone of the embodiment, FIG. 4 is a cross-sectional view of a conventional condenser microphone, and FIGS. Cross-sectional diagram of main parts,
FIG. 7 is a frequency characteristic diagram of the condenser microphone shown in FIG. 4. 1... Condenser microphone 2...
...Case 2a ...... Hole 3.
・・・・・・・・・Circuit board 4・・・・・・・・・FF
T transistor 6a...Electret film 6b...Counter electrode 7...
・・・・・・Spacer 13・・・・・・Adhesive
14... Sealant Fig. 1, Fig. 3 ± Fig. 4, Fig. 5, Fig. 6

Claims (1)

[Claims] (1) A pressure vibration detection element in which a pressure vibration detection means is arranged so as to close an opening at one end of a cylinder, characterized in that the air leakage path other than the opening of the cylinder is closed. Pressure vibration detection element.