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The invention relates to a device for improving the frequency characteristics of a transducer
capsule provided behind an earpiece having an acoustic passage opening of a handset body for a
telephone, comprising a transducer capsule and an earpiece In the front chamber between, a
device is provided in which a resonator is provided to reduce the Q of the resonance in the
frequency characteristic of the transmission volume. Industrial Applicability The frequency
characteristic of the converter film for telephones has a resonant frequency. This resonant
frequency position or profile is placed in the transmission area (300-3400 2) in order to obtain
sufficient sound volume in the design of the transducer and is flattened by suitable means. In
addition, there is an unwanted resonance peak (8 kHz) above the transmission region, which
must be reduced to such an extent that it does not disturb. It is known to do this by forming an
acoustic low pass filter from the passage (cavity quality j1) of the acoustic passage opening of the
handset and the front chamber (cavity spring). However, particularly for flat handset bodies, it is
no longer possible to obtain the volume required for the acoustic low pass filter characteristics.
What is caused by the resonance Q of the frequency response at 8 kHx, ie the harmonics of the
transducer plate, must be reduced absolutely. The problem to be solved by the invention The
object of the invention is to provide a device for reducing the Q of such resonances. SUMMARY
OF THE INVENTION According to the present invention, the front chamber is connected to at
least one ring-shaped resonance chamber formed by a notch at the inner surface of the receiver
opening, and the width of the resonance chamber is resonant It is solved by making it the same
as the wavelength of the hour frequency. The required low-pass filter characteristic is thus
formed by the ring-shaped resonance chamber. The absorption frequency is determined by: Here,
C is the velocity of sound in the air, and L is the width of the ringing resonator. On the handset
side of the handset body of the telephone, the external shape of the handset is usually configured
in a concave shape for better adaptation to the human ear. Thus, if the handset body is flat, the
central area of the handset is very thin. It is therefore advantageous for the resonance chamber
to be concentrically adjacent to the sound passage opening in the central region of the earpiece.
As a result, a resonance chamber is advantageously obtained in the region of the earpiece which
has a relatively large thickness. In order to obtain damping of harmonic oscillations with
sufficient width, it is advantageous for the resonance chamber to have a step-shaped cutout. As a
result, a plurality of absorption frequencies are obtained in which the braking characteristic
profiles overlap one another. The invention will be explained in more detail below on the basis of
two figures.
The device shown in FIG. 1 is a cross section of a transducer capsule 2 provided behind the
earpiece l. The handset 1 is a component of the handset body not shown in detail here. The
transducer capsule has a casing 3 in the chamber of which a transducer plate 7 held between the
supports 4, 5 and provided with a piezoelectric layer 6 is arranged. The converter plate 7 divides
the chamber of the casing 3 into a rear chamber 8 and a front chamber 9. In the anteroom 9, an
acoustic passage opening 12 is provided on the receiver opening side. A plate 10 provided with a
cylindrical projection 11 surrounds the sound passage opening 12, and the plate is in the form of
a ring and the receiver opening closely in contact with the projection 21 formed on the inner side
of the receiver opening is It has a concave outer shape on the outside. An acoustic passage
opening 13 is disposed in the central region. A ring-shaped notch 14 is provided on the inner
side of the receiver opening concentrically with the opening. This notch is connected to the
antechamber 9 via an intermediate chamber 15. The notch 14 is configured in a step-like
manner, and two absorption frequencies can be set and adjusted. The absorption frequency is
determined by the width of the notch. The width here is, for example, for the absorption
frequency. The waveform diagram of FIG. 2 shows the tolerance range for the frequency curve of
the device of FIG. 1 as a function of volume with the line 16.17. The tolerance area is between
lines 16 and 17. The curve represented by position 18 is the profile of the device of FIG. 1
without braking means. The curves represented by positions 19 and 20 are frequency profiles
with the resonance chamber shown in FIG. This frequency profile is within the tolerance range.
Effect of the Invention According to the present invention, even when the handset body is flat
and the volume necessary for the conventional acoustic low pass filter can not be obtained, the
resonance Q of the transmission frequency characteristic can be reduced.
Brief description of the drawings
FIG. 1 is a cross-sectional view of an electro-acoustic transducer provided behind the receiver
opening of the handset body, and FIG. 2 is a waveform diagram showing the frequency
characteristic curve with and without the braking means.
■ ...... Receiver socket 1.2 · · · converter capsule, 3 · · · casing, 4,5 · · · support body, 6 · · ·
piezoelectric layer, 7 · · · converter plate, 8 · · · Rear chamber 9, front chamber 10, plate-like body,
11 cylindrical projection, 12.13 acoustic passage opening, 14 ring-shaped notch, 15 Intermediate
chamber, 16.17 ... Permissible region, 18 ... Frequency characteristics when no braking treatment
is taken 19, 20. ... Frequency characteristics when taking a braking treatment, 21 ... projection, L
... width,-21 .... Part F [G2 lHz −
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