JPH0199531A - Probe for measuring dynamic behavior of auris media - Google Patents

Abstract

PURPOSE:To measure a minute change for absolute acoustic pressure and an absolute phase difference of a human eardrum against a continuous vibration frequency by a method wherein, a hard and thick material is used as a main body, the length thereof is so set as being capable to be attached to an external auditory meatus but as short as possible, while boring acoustic conduction hole directly on the main body. CONSTITUTION:A sinusoidal wave signal from an oscillator 20 which frequency changes in the range 0.1-2.0kHz is amplified at an amplifier 22, converted into a sound of constant sound pressure by a earphone 10 located within a main probe body 1, passes through one side acoustic conduction hole 6, and is conducted into an external auditory meatus 10. In the meanwhile, an air pump 23 is communicated to the inside of the external auditory meatus through a one side or the other side acoustic conduction hole of the probe main body, and the pressure is boosted or reduced within the range of +200--200dapa. While the change of the acoustic pressure within the external auditory meatus is measured through a microphone 8 positioned inside the probe main body, the phase difference between the earphone and the microphone is measured. If considering the probe main body being an insertion part for the external auditory meatus as a cantilever, it is found necessary that the primary natural frequency f1, in this case, should be a measured frequency or more at least. From this, it is required that the length of the main body is as short as possible, with small density rhoand sufficient thick thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a probe for measuring middle ear dynamic characteristics that can measure minute changes in middle ear dynamic characteristics.

``Prior art'' Conventionally, this type of probe for measuring middle ear dynamic characteristics has three stainless steel pipes that penetrate and are fixed inside the external auditory canal insertion part that is inserted into the external auditory canal, and a silicon tube is attached to the protruding end of each of these pipes. They were connected and communicated with a microphone, a probe earphone, and a stimulation earphone, respectively, and a pressure tube was branched and communicated with the tube connected to the stimulation earphone ν.

``Problems to be Solved by the Invention'' However, in the conventional probe, a fairly long tube of 15 to 22 aa was used between the insertion part of the ear canal and the microphone or earphone. - The theoretical characteristics of the sound pressure in a closed acoustic tube are almost flat against changes in frequency, as shown by the solid line characteristics (A1) in Figure 3, and the theoretical characteristics of the phase difference are shown in Figure 4. It is desirable that the frequency increases linearly with respect to changes in frequency, as shown in the solid line characteristic (A2). However, in the case of the conventional type in which long tubes are connected, due to the low acoustic resonance within the tubes, the sound pressure measurement curve becomes like the dotted line characteristic (C) in Figure 3, and the phase difference characteristic becomes As shown in the dotted line characteristic (C2) in FIG. 4, there is a problem in that the characteristic changes greatly with frequency within the audible range. Also.

Conventionally, grooves can be seen in tubes whose length has been shortened to several digits, but the length of the tube is still long.
Because the tube is made of a soft material such as vinyl, the wall thickness of the tube is thin, and the probe body is made of a soft material such as plastic, the mechanical resonance point is low and the sound still remains within the audible frequency range. There was a problem in that large peak values were observed in the pressure characteristics and phase difference characteristics. Therefore, conventional probes cannot measure the minute frequency characteristics of the human eardrum.

"Means for Solving the Problems" The present invention was made to solve the above-mentioned problems, and it connects an air pump to either one of the two sound guide holes in the probe body to connect the air pump to one of the two sound guide holes in the probe body. The oscillation signal in the audible range is converted into sound at a constant sound pressure using an earphone, and the sound is supplied to the external auditory canal through one of the sound guide holes in the probe main body. In a probe for measuring middle ear dynamic characteristics that measures pressure changes and phase differences between a microphone and an earphone, the probe body is made of a hard and thick material, and the length is attached to the ear canal. The probe body is made as short as possible, and a sound guiding hole is formed directly in the probe body.

"Operation" A sine wave signal from an oscillator whose frequency varies in the range of 0.1 to 2.0 KHz is amplified by an amplifier, converted to sound with a constant sound pressure by the earphone inside the probe body, and is transmitted through one sound guide hole. is guided into the external auditory canal. In addition, an air pump is communicated with the ear canal through one or the other sound guide hole of the probe body to pressurize or depressurize it in the range of +200 daPa to -200 daPa6.Then, the sound pressure change in the ear canal is measured using the microphone inside the probe body. At the same time, the phase difference between the earphone and microphone is measured.

"Example" An embodiment of the present invention will be described below based on the drawings.

In Fig. 1, (1) is the probe body, which is made of a hard material such as metal or ceramic, and has a cylindrical ear canal insertion part (2) at the tip, and a conical part (3) from the middle. ) and has a total length of about 19 oa. The outer diameter of the external auditory canal insertion part (2) is about 3 to 4
Two semicircular sound guide holes (5) and (6) are formed in the shape of Iφ and separated by a center wall (4), and the sound guide holes (
5) The inner diameter of (6) is approximately 2 to 3 mm. One sound guide hole (5) is bent at a right angle at a position with a length of about 14 nm and communicates with the microphone mounting hole (7) of the conical part (3), and this microphone mounting hole (7) is connected to the microphone (8). After mounting, it is molded (9) with resin, glass, etc. The other sound guide hole (6) penetrates to the base end and communicates with the earphone (10), and the conical part (3) in the middle connects the air hole (11).
) are branched and connected to an air pipe (12) containing an acoustic filter (15).

Note that the air hole (11) may be one of the sound guide holes (5).

The earphone (10) is entirely covered with a cover (13) and molded (14). You can also use earphones (
10) and a microphone (8) are connected to the sound pressure and phase difference measurement circuit shown in FIG. 5, and the air pipe (12) is connected to an air pump.

The probe (16) configured as described above has an earplug (17) attached to the outer periphery of the external auditory canal insertion portion (2), and is inserted into the external auditory canal (18) of the subject to perform measurements. (19) is the eardrum. To measure, first, a sine waveform signal whose frequency f is varied in the range of 0.1 to 2.0 KHz by the adjusting means (21) is sent from the oscillator (20) of the measuring circuit shown in Fig. 5 to the power amplifier. (22) through the probe body (1
) is sent to the earphone (10) in this earphone (10).
), the sound is converted into sound at a constant sound pressure and guided into the external auditory canal (18) through one of the sound guide holes (6) of the probe body (1).

Also, the air from the air pump (23) is sent to the air pipe (12).
, an acoustic filter (15), and a sound guide hole (6) in the probe body (1) are supplied to the external auditory canal (18), and the inside of this external auditory canal (18) is heated from +200 daPa to -200 daP.
Pressure is increased or decreased within the range a. Then, the ear canal (
18) is detected and measured by a volume detection circuit (26) via a preamplifier (24) and a filter (25), and a phase difference meter measures the phase difference between the earphone (10) and microphone (8). (27). This information is temporarily stored in the digital storage oscilloscope (28) and then output to the X-Y recorder (29).

In Fig. 5, (30) is a pressure gauge, (31) is an absolute sound pressure change (SPL) display section, (32) is a frequency display section, (33) is a pressure display section, and (34) is a pressure gauge. The volume detection value display section (35) is a phase difference display section.

Next, the theoretical basis for why the probe body (1) according to the present invention must have the shape shown in FIG. 1 and be made of a hard material will be explained.

If the probe body (1), which is the insertion part of the ear canal, is considered as a single cantilever beam, the natural primary frequency f1 in this case is as follows. Here, Q, A, and I are the length, cross-sectional area, and second moment of area of the probe body (1), respectively, and E and ρ are the Young's modulus and density of the material, respectively.

In the above equation, since k is a constant, it is necessary to set f to a value that is at least equal to or higher than the measurement frequency, specifically, equal to or higher than 2000)1z. From this, (1) □ must be large, that is, the length must be as short as possible, and the material must be hard with a large Young's modulus E.

is required.

The probe of the present invention is constructed to satisfy these requirements.

"Effects of the Invention" Since the present invention is configured as described above, it is possible to measure minute absolute sound pressure changes and absolute phase differences of the human eardrum with respect to continuous excitation frequencies. Incidentally, the dynamic characteristics of the probe according to the present invention in an acoustic tube with one end closed are the sound pressure characteristic (B1) shown by the chain line in Figure 3 and the phase difference characteristic (B1) shown by the chain line in Figure 4.
As is clear from B2), it agrees extremely well with the theoretical value.

Further, FIG. 6 shows the sound pressure characteristics when the human ear with a normal eardrum is determined using the probe of the present invention, and FIG. 7 similarly shows the phase difference characteristics.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the probe for measuring middle ear dynamic characteristics according to the present invention, FIG.
The figure shows the characteristics of sound pressure in an acoustic tube with one end closed, Figure 4 shows the characteristics of phase difference in an acoustic tube with one end closed, Figure 5 shows the measurement circuit diagram, and Figure 6 shows the characteristics of the human Sound pressure characteristics diagram at the ear, No. 7
The figure is a phase difference characteristic diagram of the human ear. (1) Probe body, (2) Ear canal insertion part, (3) Conical part, (4) Center wall, (5)
(6)...Sound guide hole, (7)...Microphone mounting hole, (8)...Microphone, (9)...Mold,
(10)...Earphone, (11)...Air hole, (
12)...Air pipe, (13)...Cover, (14)
)...mold, (15)...acoustic filter, (
16)...Probe, (17)...Earplugs, (18)
... external auditory canal, (19) ... eardrum.

Claims (4)

[Claims] (1) Connect an air pump to either one of the two sound guide holes in the probe body to pressurize or depressurize the external auditory canal;
An oscillation signal in the audible range is converted into sound with a constant sound pressure using an earphone, and the sound is supplied to the ear canal through one of the sound guide holes in the probe body. In the probe for measuring middle ear dynamic characteristics, the probe body is made of a hard and thick material, and the length is as short as possible within the range that allows it to be installed in the external auditory canal. A probe for measuring middle ear dynamic characteristics is formed as described above and has a sound guiding hole directly formed in the probe body. (2) The probe for measuring middle ear dynamic characteristics according to claim 1, wherein the sound guide hole communicating with the earphone and the sound guide hole communicating with the microphone are semicircular holes facing each other with a partition wall in the center. (3) The probe for measuring middle ear dynamic characteristics according to claim 1, wherein the probe body is made of stainless steel, iron, or ceramic. (4) The length of the sound guide hole in the probe body is 10 to 30 mm.
A probe for measuring middle ear dynamic characteristics according to claim 1.