JPS6133314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a conference telephone device, more particularly a conference telephone device with good sound quality, sufficient volume, omnidirectional in both transmitting and receiving modes, for conference calls or public addresses. The present invention relates to an integrated speaker and microphone device that is satisfactory both in appearance and in practicality when used in the field.

Conventional conference phone devices have several drawbacks that depend on the shape of the device. Speakers are often more visible than microphones, creating human behavior problems in teleconferences where users speak into the speaker rather than the microphone. In such cases, the level and quality of the audio signal is degraded. Also, in some devices, the microphone is omnidirectional so that the signal level and quality changes when the speaker changes in the case of an indoor conference. Speakers and/or microphones are highly visible;
Generate some kind of response by the speaker.

Although the present invention is omnidirectional, there is sufficient acoustic separation between the speaker and the microphone.
To provide a device that has excellent aesthetics and does not give an unsightly appearance when used in a meeting.

The speaker and microphone are on a common longitudinal axis, with the speaker facing upward and the microphone facing downward. The microphone is located in the center of the sloping surface and is structured to avoid standing waves and other distortions. The speaker and microphone are omnidirectional and have good acoustic isolation. Existing electronic circuitry used in existing speakerphones can be installed into the housing of the device and connected to the telephone system, and telephone dials and other controls can be installed in or on the housing. . It is also possible to interconnect several loudspeaker and microphone devices. By using an audio switching device, which is part of a normal electronic circuit, a designated device functions as a microphone and the other device functions as a speaker.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be easily understood on reading the following description of some embodiments, by way of example only, with reference to the accompanying drawings in which: FIG.

The apparatus illustrated in FIGS. 1-4 includes a housing 10. The apparatus shown in FIGS. As can be seen in FIGS. 1 and 4, this housing 10 forms a longitudinally elongated enclosure, and as can be seen in FIGS. 2 and 3, the cross section perpendicular to the longitudinal axis is square. In the illustrated embodiment, the size of the square cross section is the same as that of the speaker 11.
is large enough to enclose the housing 10
An opening 13 is provided in the upper surface 12 at a position corresponding to above the speaker 11. The loudspeaker 11 operates within an enclosed chamber 14. The chamber 14 is closed at the bottom by a diaphragm 15.

Attached to diaphragm 15 is microphone housing 16 . The microphone housing has a downwardly opening opening 17, and a microphone 18 is mounted facing downwardly within the opening 17. The microphone housing has an inclined surface 19 extending outwardly and upwardly into the housing 10. The angle of inclination of surface 19 with respect to the horizontal plane is important.

The device can be placed on a horizontal surface with the microphone close to this surface. Legs 20 are used to support the device with the desired spacing between the microphone and the support surface. The type of support surface affects the microphone. Microphones are effective when placed on a hard surface, such as the wooden surface of a table. However, if you place it on a carpeted floor or table cloth, the microphone's sensitivity will decrease, especially in the high frequency range. For example, a rigid base member 21 can be attached to the legs 20 in order to make the device independent of the type of support surface. The provision of the base 21 lends itself to any type of mounting of the device, for example on the floor, on a table, on a wall or on a ceiling.
Sensitivity and omnidirectionality are not compromised.

The size of the speaker can be various, but 6
The inch (15.2cm) speaker has a suitable volume output,
I found that the sound quality was also satisfactory. Smaller speakers will lose bass and have lower volume.

There are various parameters that must be considered when designing this device. The acoustic isolation between speaker 11 and microphone 18 must be sufficient. This limits the peripheral distance between the centerline of the loudspeaker and the centerline of the microphone - that is, the distance indicated by arrowed dashed line 25 in Figure 1 - to a minimum of approximately 15
It was found that this can be achieved by making the distance 38cm (38cm). This distance can be made shorter, but as the distance decreases below approximately 15 inches (38 cm), the desired level of acoustic isolation begins to decrease. The gap between the front or inlet of the microphone and the supporting surface - distance "a" in Figure 1 - is
The angle of inclination of the inclined surface 19 with respect to the support surface - the angle "α (ho)" in Fig. 1 is approximately 0.5 inch (1.27 cm).
It has to be done to a certain degree.

Physical Separation - Distance from the centerline of the speaker to the centerline of the microphone around the circumference of the case.
is of course a function of the width and height of the housing. The housing can be made tall and thin, or short and thick. There is no problem with increasing this distance, but this is a matter of appearance;
Also, consideration must be given to ensuring that it does not cause any discomfort. For example, if you are in a meeting and the attendees are sitting around a table, and you want to place it on the table,
It is desirable that the housing does not prevent attendees from seeing each other. Also, if it is made too thin, only a portion must be enlarged for the purpose of the speaker.

Mounting the speaker and microphone on a common longitudinal axis is desirable because the acoustic separation is symmetrical around the housing. Another very important feature is that the speaker faces upward and is non-directional, and similarly the microphone faces downward and is non-directional. This eliminates the need for multiple speakers and/or microphones, and does not result in directional sensitivity differences as is the case with other types of conference calls.

Due to the downward facing microphone facing a hard surface and the microphone being mounted in a flat plane, a strong resonance occurs due to standing waves at the entrance of the microphone. By tilting the surface surrounding the microphone, such resonances can be avoided. This means that the device itself does not add to the resonance of the room in which it is used, and a substantially uniform frequency-microphone response results. The slope of the surface can be varied, and it was found that approximately 30 degrees is optimal. However, a change of ±5 degrees is easy. The inclined surface 19 is preferably flat, but may also be slightly curved. In this case, undesirable frequency irregular components are introduced.

As mentioned above, the vertical distance between the entrance of the microphone and the surface facing the microphone (such as the base 21 or the top surface of a table if no base 21 is provided) is important. Satisfactory results are obtained when this spacing is approximately 0.5 inches (12.7 cm) ± 10%; as the distance deviates from this value, the efficiency of the microphone decreases rapidly. Outside this range of values, the frequency response of the microphone becomes unacceptably uneven.

The distance for physical separation is preferably on the order of 15 inches (38 cm). Shorter than this value increases acoustic feedback from speakers and microphones. This distance is important because low frequencies, for example below 100Hz, easily diffract around obstacles. As frequency increases, the increased directivity of the loudspeaker and the effect of housing "shading" in the microphone area offset the increase in microphone sensitivity with frequency, similar to the case with telephone handsets. Ru. A substantially constant acoustic isolation is thus achieved and the acoustic stability of the device is independent of frequency. This distance can be increased, but then the appearance issues and non-obtrusive features mentioned above become the focus.

Although the opening above the loudspeaker is shown open in FIGS. 2 and 3, this is usually closed by a grid or screen to avoid damage to the loudspeaker.

Using a microphone that is sensitive to airborne sound but insensitive to mechanical vibrations allows the speaker and microphone to be housed in a common housing. Such a microphone is an electret microphone. This is because electric microphones do not feel mechanical vibrations. This simply and economically solves the problem of acoustic feedback due to solid state transmission through the housing.

With the geometry shown and the favorable physical characteristics described above, the acoustic isolation will exceed 20 decibels. This results in stable acoustic operation of the device with a switch loss of 50 dB (a common technique for avoiding feedback in speakerphones). Because of this, the effect of voice switching is hardly noticeable.

For long subscriber loops, very high attenuation occurs near the high end of the telephone frequency range above 1000 Hz. A resonator 26 mounted at the entrance of the microphone enhances this high end of the frequency range.
That is, it produces a harder sound, making the audio signal clearer and easier for the listener to distinguish. The vibrator 26 is a flat disk having a rim around its periphery, and has an opening 27 in the disk portion. The openings may be slots, holes, or other shapes.

This device has a variety of uses. This device can be integrated into an existing speakerphone set using the set's circuitry. Also, since each device can have its own circuitry built into the housing and the various devices can be interconnected, it can also be used as a combined conferencing and public address system. The device closest to the person speaking is then switched to the microphone side, and the remaining devices are switched to the speaker side so that everyone can hear what is being said.

A control device may also be provided, for example a volume and/or sound quality control device. This device can be connected directly to a telephone system without an intervening speakerphone device. In such a case, the interior portion 28 of the housing, the outline of which is shown in dashed lines in FIGS.
A speakerphone circuit can be installed on the
Dial 29 can be mounted on one side along with various control buttons 30 and control knobs 31.

Although the devices shown and described have a square cross-sectional shape when viewed from the top or bottom, other cross-sectional shapes are possible. Cylindrical housings or polyhedral housings such as hexagonal or octagonal housings can be used. Figure 5 shows the cylindrical housing 3.
5 is a perspective view of the device with 5. FIG. On this side as shown, the outer casing extends to just below the eyelashes and surrounds the microphone housing. The microphone is surrounded by an inclined surface as in the previous example. A perforated portion 36 of the housing 35 surrounds the microphone portion.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a shaped device. FIG. 2 is a view taken in the direction of arrow A in FIG. 1, with the bottom plate removed. FIG. 3 is a plan view of the end of the speaker. FIG. 4 is a sectional view showing the positions of the switch and telephone dial. Fifth
The figure is a perspective view of an alternative configuration of the device. 10 and 35... Housing, 11... Speaker, 18... Microphone, 19... Inclined surface,
20... Legs, 21... Base member, 26... Resonator, 28 and 29... Electric circuit means, 30 and 31... Electric control member, 36... Portion with hole.

Claims (1)

[Claims] 1 A telephone device for use in a conference room having a housing, a speaker mounted on the upper end of the housing and a microphone mounted on the lower end of the housing, both facing away from each other on a common axis. The circumferential distance from the centerline of the speaker around the outside of the housing to the centerline of the microphone is approximately
a speaker and microphone that are 15 inches (approximately 38 cm) in diameter and extend upwardly and outwardly from the microphone toward the periphery of the housing at an angle of approximately 30 degrees ± 5 degrees with respect to a plane perpendicular to the common axis; and a support means for supporting the housing such that the front surface of the microphone is approximately 0.5 inches ± 0.05 inches from a surface perpendicular to the common axis. death,
A telephone device characterized in that the microphone is of a type that senses only air-borne sound and does not sense mechanical vibration.