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BACKGROUND OF THE INVENTION It is always a problem in car phones that the noise generated
by the vehicle interferes with the communication. This problem is, of course, more pronounced
than the microphone being far from the driver. It is desirable to place the microphones, for
example, on or next to the instrument panel, as traffic can be made more secure by minimizing
the number of components associated with the use of the phone away from the driver.
The following apparatus can be used to make such a microphone selective, whereby relatively
more speech is uttered and less irrelevant noise is picked up. It is. Of course, this solution can
also be applied to other types of phones, such as office speakerphones.
SUMMARY OF THE INVENTION The above-mentioned problems are solved by the present
invention, as described in claim 1 above, which provides an apparatus for selectively silencing
ambient noise for use with a microphone. Advantageous design variants of the invention are
specified in the dependent claims that follow.
BEST MODE FOR CARRYING OUT THE INVENTION The present invention consists of a tube
coated on the inside with a sound-absorbing surface such as floc (which can also be attached
electrostatically with short longitudinal fibers like scraps). The open end of the tube is directed to
the driver's mouth. A microphone is placed at the closed end of the tube opposite to it. By means
of this surface coating, the sound waves striking the opening of the tube at an angle are silenced,
while the sound waves traveling along the length of the tube are transmitted to the microphone.
Alternatively, the microphone may be mounted inside the tube by coating the outside with flocks.
Contact between the two flocked coated surfaces results in a high friction bond with acoustical
properties. In addition, the microphone may be installed in a sound absorbing foam (foaming)
material, or may be suspended in an elastic material that does not transmit sound waves.
Several paralleled tubes may be provided to further increase the selective output of the device, or
one tube may be longitudinally split by internal partitions.
The output may be amplified by shaping the bottom of the tube like a parabola, so that the sound
can be concentrated towards the microphone.
For example, a friction joint may be provided at the end of the tube in order to be able to adjust
the direction of the whole device.
This may be a ball joint or a pin joint.
A simple way to get enough friction to easily change the direction of the tube and to avoid the
risk of being changed by vibration is to coat the surface of the joint with flocks. This also
prevents cracking when the position changes.
The invention is not restricted to the model of the design described here, but can be freely
modified within the framework of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a lateral side view of the device according to the invention. FIG. 2 is a cross-sectional
perspective view showing another model of the invention in which several tubes are arranged
close to one another in parallel. FIG. 3 shows another model of the invention in which the tube is
divided into several sound paths by longitudinal partitions. FIG. 4 shows yet another model of the
invention in which the tube is surrounded by a concentric outer tube coated internally with
sound absorbing material.