CN100531259C

CN100531259C - Voice communications apparatus

Info

Publication number: CN100531259C
Application number: CNB2003801074892A
Authority: CN
Inventors: 高田真资; 青柳弘美; 秋江一良
Original assignee: Oki Electric Industry Co Ltd
Current assignee: Oki Electric Industry Co Ltd
Priority date: 2002-12-27
Filing date: 2003-12-24
Publication date: 2009-08-19
Anticipated expiration: 2023-12-24
Also published as: JP2010246139A; JP5003794B2; CN1732675A

Abstract

Voice communications apparatus intervenes between a telephone set and a broad-band transmission path that has a communication band broader than a voice band limited by the transmitter and receiver characteristics of the telephone set. The voice communications apparatus includes a transmitter frequency characteristic corrector circuit for correcting the frequency characteristic of a signal input from the telephone set, and a receiver frequency characteristic corrector circuit for correcting the frequency characteristic of a signal to be input to the telephone set.

Description

Voice communication apparatus

Technical Field

The present invention relates to a voice communication apparatus, and more particularly, to a voice communication apparatus embedded in or adapted to a telephone set, and a voice communication system including the same.

Background

Currently, VoIP (voice over internet protocol) such voice communication using the internet or a similar IP (internet protocol) network is being expanded. Even for voice communication using an IP network, it is necessary to transmit a voice signal whose frequency band is limited to within 4kHz, that is, a so-called telephone band signal. This is because voice signals above 4kHz cannot be input to a cable transmission path or a conventional public switched telephone network. In contrast, the IP network is not restricted by such a limitation, and it can implement voice communication using a wide frequency band, i.e., signals in a frequency band above 4 kHz.

More specifically, as shown in fig. 2, unlike an IP telephone set which can be connected only to an IP network, a conventional telephone set has a transmitter characteristic that limits a broadband signal input to a microphone to 4kHz or less. Also, as shown in fig. 2, the receiver characteristic of the conventional telephone set limits the signal received via the transmission path to 4kHz or less before outputting the signal from the earphone of the speaker. As a result, even if the transmission path allows transmission of signals above 4kHz like an IP network, the obtainable voice quality is not higher than in the case where the transmission path is a conventional public switched telephone network. The transmitter and receiver characteristics described above are implemented, for example, with band pass filters.

In the above environment, unless the telephone set itself has transmitter and receiver characteristics capable of adapting to a wide frequency band, high-quality communication using a wide-band signal cannot be realized by means of an IP network. However, as described above, for many conventional telephone sets, since the transmitter and receiver characteristics limit the frequency band to 4kHz or less, they cannot enjoy high voice quality peculiar to IP networks or similar transmission paths that allow broadband signals.

Disclosure of Invention

An object of the present invention is to provide a voice communication apparatus which can realize high voice quality even when a conventional telephone set uses an IP network or the like transmission path which allows transmission of a broadband signal, and a voice communication system including the same.

According to the present invention, there is provided a voice communication apparatus interposed between a telephone set and a broadband transmission path having a communication band wider than a voice band limited to a transmitter characteristic and a receiver characteristic of the telephone set, the apparatus comprising: a transmitter frequency characteristic corrector circuit which has a first correction frequency characteristic and corrects a frequency characteristic of a signal input from the telephone set; and a receiver frequency characteristic corrector circuit which has a second correction frequency characteristic and corrects the frequency characteristic of the signal input to the telephone set; wherein the first correction frequency characteristic makes a synthesized frequency characteristic of the transmitter characteristic and the first correction frequency characteristic flat in a communication band of the broadband communication path; the second correction frequency characteristic makes the composite frequency component of the receiver characteristic and the second correction frequency characteristic flat in the communication band of the broadband communication path.

The voice communication apparatus of the present invention is interposed between a telephone and a broadband transmission path having a communication band wider than a voice band limited by the transmission and receiver characteristics of the telephone. The voice communication apparatus includes a transmitter frequency characteristic corrector circuit for correcting the frequency characteristic of a signal input from the telephone, and a receiver frequency characteristic corrector circuit for correcting the frequency characteristic of a signal input into the telephone.

Preferably, the transmitter frequency characteristic corrector circuit has a first correction frequency characteristic whereby a synthesized frequency characteristic of the transmitter characteristic and the first correction frequency characteristic is made flat in a communication band of the broadband communication path, and the receiver frequency characteristic corrector circuit has a second correction frequency characteristic whereby a synthesized frequency component of the receiver characteristic and the second correction frequency characteristic is made flat in the communication band of the broadband communication path.

In addition, a voice communication system comprising the voice communication equipment is also provided.

According to the present invention, there is provided a voice communication system for connecting two telephone sets via a broadband communication path having a communication band wider than a voice band limited to a transmitter characteristic and a receiver characteristic of each of the two telephone sets, wherein each of the two telephone sets is connected to the broadband communication path via a voice communication device, the voice communication device comprising: a transmitter frequency characteristic corrector circuit which has a first correction frequency characteristic and corrects a frequency characteristic of a signal input from the telephone set; and a receiver frequency characteristic corrector circuit which has a second correction frequency characteristic and corrects the frequency characteristic of the signal input to the telephone set; wherein the first correction frequency characteristic makes a synthesized frequency characteristic of the transmitter characteristic and the first correction frequency characteristic flat in a communication band of the broadband communication path; the second correction frequency characteristic makes the composite frequency component of the receiver characteristic and the second correction frequency characteristic flat in the communication band of the broadband communication path.

Drawings

The objects and features of the present invention will become more apparent upon review of the following detailed description when taken in conjunction with the drawings in which:

FIG. 1 is a schematic block diagram illustrating an embodiment of a voice communication system in accordance with the present invention;

FIG. 2 is an exemplary depiction of transmitter and receiver characteristics typical of a conventional telephone set;

FIGS. 3A and 3B are schematic block diagrams showing certain portions of the voice communications apparatus included in the embodiment shown in FIG. 1;

fig. 4A, 4B, and 4C are diagrams useful in understanding the transmitter frequency characteristic corrector function included in the embodiments;

fig. 5A, 5B, and 5C are diagrams useful in understanding the receiver frequency characteristic corrector function included in the embodiments;

FIG. 6 depicts specific frequency characteristics of an input speech signal that may be used to understand operation of an embodiment;

fig. 7 is a schematic block diagram showing a transmission frequency characteristic corrector according to an alternative embodiment of the present invention;

fig. 8A, 8B, and 8C are graphs depicting correction frequency characteristics of the correction filter shown in fig. 7;

FIG. 9 is a schematic block diagram illustrating another alternate embodiment of the present invention;

FIG. 10 is a schematic block diagram similar to FIG. 9 showing another alternate embodiment of the present invention; and

FIG. 11 is a schematic block diagram similar to FIG. 9 showing another alternate embodiment of the present invention.

Detailed Description

Referring to fig. 1 of the drawings, the preferred embodiment of a voice communication system in accordance with the present invention is indicated generally by the reference numeral 1. As shown, the voice communication system 1 is adapted to allow voice signals to be communicated via the IP network 2 between a particular two of a plurality of end nodes, not shown, interconnected with the network 2.

One of the end nodes comprises a voice communication device 10 and a telephone set 11 accommodated in the voice communication device 10. Likewise, the other end node includes a voice communication device 20 and a telephone set 12 housed in the voice communication device 20. It should be noted that the telephone sets 11 and 12 may also be implemented by means of fax machines or other types of telephone service equipment, for example, as long as they transmit signals in the voice band limited by the conventional public switched telephone network.

In the exemplary embodiment, telephone sets 11 and 12 are conventional telephone sets that have transmitter and receiver characteristics that limit the frequency band to 4kHz or less. Therefore, the configuration inside the telephone sets 11 and 12 is not shown in fig. 1, and will not be specifically described.

By configuring each of the voice communication apparatuses 10 and 20, it is possible to process voice signals in a relationship matching broadband communication available to the IP network 2. Fig. 3A and 3B show a transmitter system and a receiver system, respectively, that are unique to each of the voice communication devices 10 and 20.

As shown in fig. 3A, the transmitter system of the voice communication apparatus 10 or 20 includes a transmitter F (frequency) characteristic corrector circuit 31 and a voice signal-to-IP packet converter circuit 32 which are interconnected in the manner shown. The transmitter F characteristic corrector circuit 31 is realized by, for example, an analog or digital filter, and is adapted to make the frequency of the voice signal output from the telephone set 11 or 12 associated with the transmission line flat over the entire voice frequency band. Fig. 4A exemplarily depicts a specific voice signal frequency characteristic limited to a frequency band in consideration of a conventional public switched telephone network applicable to the telephone set 11 or 12. As shown in fig. 4B, the transmitter F characteristic corrector circuit 31 raises the limited-band gain shown in fig. 4A to some extent, whereby an unlimited frequency band can be restored. Fig. 4C depicts correction frequency characteristics specified for the transmitter F characteristic corrector circuit 31.

Although the voice band range shown in fig. 4A, 4B, and 4C is from 0Hz to 8,000Hz, this voice band range is only illustrative. Further, the transmitter F characteristic corrector circuit 31 does not necessarily correct the frequency characteristic to be completely flat, but may be distorted to some extent.

In general, the types or characteristics of the telephone sets 11 and 12 connected to the voice communication apparatuses 10 and 20, respectively, are not necessarily fixed. In view of this, it is preferable to configure the transmitter F characteristic corrector circuit 31 so as to be able to change the correction frequency characteristic, whereby an engineer can operate the adjuster section to adjust the characteristic of the installation site.

The voice signal-to-IP packet converter circuit 32 is adapted to convert the voice signal whose frequency characteristic is corrected by the transmitter F characteristic corrector circuit 31 into an IP packet.

On the other hand, the receiver system of the voice communication apparatus 10 or 20 shown in fig. 3B includes an IP packet-to-voice signal converter circuit 41 and a receiver F characteristic corrector circuit 42 which are interconnected in the manner shown. The IP packet-to-voice signal converter circuit 41 is adapted to decompose the IP packets from the IP network 2 so as to recover the original voice signal. The voice signal recovered in this manner has its frequency characteristic corrected by the transmitter F characteristic corrector circuit 31 so as to be similar to or correspond to the frequency characteristic of the voice signal output from the corrector circuit 31.

The receiver F characteristic corrector circuit 42 is implemented by, for example, an analog filter. Considering the receiver characteristic of the associated telephone set 11 or 12, the receiver F characteristic corrector circuit 42 is adapted to raise beforehand to some extent the frequency band component attenuated by the receiver characteristic of the telephone set 11 or 12. For example, as shown in fig. 4B, in an application in which the telephone set 11 or 12 has the receiver characteristics selected in consideration of the conventional public switched telephone network shown in fig. 5A, the receiver F characteristic corrector circuit 42 raises the frequency band component attenuated by the above-mentioned receiver characteristics in advance for the frequency characteristics of the voice signal output from the IP packet-to-voice signal converter circuit 41, thereby generating a voice signal having the frequency characteristics shown in fig. 5B. Fig. 5C shows the correction frequency characteristic specified for the receiver F characteristic corrector circuit 42. Also, although the voice band is shown in fig. 5A, 5B, and 5C as ranging from 0Hz to 8,000Hz, this voice band is merely illustrative.

As described above, the types or characteristics of the telephone sets 11 and 12 connected to the voice communication apparatuses 10 and 20, respectively, are not necessarily fixed. Therefore, it is preferable to configure the receiver F characteristic corrector circuit 42 so as to be able to change the correction frequency characteristic, whereby an engineer can adjust the above-mentioned characteristics of the installation site by operating its adjuster part.

In operation, when a user of one of the telephone sets 11 intends to transmit a voice signal to the other telephone set 12, the voice uttered by the user is picked up by the microphone or transmitter 11S shown in fig. 1, for example, and is thereby converted into an electronic voice signal. Subsequently, in the telephone set body 11B of the transmitting station 11, a telephone circuit, not shown, limits the voice signal band in a matched relationship with the applicable conventional public switched telephone network.

If the microphone 11S outputs a voice signal having flat frequency characteristics in the entire voice frequency band, for example, the frequency bands including 8kHz and below 8kHz as shown in fig. 6, the voice signal thus limited in frequency to the telephone set body 11B will have low frequency components below 300Hz and including 300Hz, and attenuated high frequency components above 3,400Hz and including 3,400Hz, as shown in fig. 4A. The voice signal output from the telephone set body 11B is input to the voice communication apparatus 10 in turn.

Referring to fig. 4C, in the voice communication apparatus 10, the transmitter F characteristic corrector circuit 31 corrects the input voice signal frequency characteristic in accordance with its own correction frequency characteristic. As a result, as shown in fig. 4B, a voice signal whose frequency characteristic is flat in the entire voice band is output from the transmitter F characteristic corrector circuit 31.

Subsequently, the voice signal-to-IP packet converter circuit 32 converts the voice signal thus corrected by the transmitter IF corrector circuit 31 into an IP packet and transmits it to the IP network 2.

These IP packets transmitted via the IP network 2 are input into another voice communication apparatus or a receiving station 20. In the voice communication apparatus 20, the IP packet-to-voice signal converter circuit 41 decomposes the IP packets arriving in this manner to restore the original voice signal, and passes the restored voice signal to the receiver F characteristic corrector circuit 42. Although the restored voice signal has similar frequency characteristics to those of the signal shown in fig. 4B, the receiver F characteristic corrector circuit 42 having the corrected frequency characteristic in fig. 5C enhances those frequency band components attenuated by the receiver characteristic, thereby outputting a voice signal having the frequency characteristic in fig. 5B. And the resulting speech signal is fed to the receiving telephone set 12.

The telephone set body 12B included in the receiving telephone set 12 attenuates the high-frequency and low-frequency components of the input voice signal in accordance with its receiver characteristics. However, since the receiver F characteristic corrector circuit 42 has raised the gain of the above-mentioned frequency components of the voice signal at the time of reception of the voice signal by the receiving telephone set 12, the voice signal is output from the telephone set body 12B so that the frequency characteristics that become flat as shown in fig. 6 actually correspond to the voice signal acquired by the transmitting telephone set 11. A voice signal having such a frequency characteristic is output from a receiver such as an earphone or speaker 12R included in the telephone set 12.

As described above, in the exemplary embodiment, even if voice communication via the IP network or the broadband transmission path 2 is maintained between the telephone sets 11 and 12 belonging to the conventional public switched telephone network, since the voice communication apparatuses 10 and 20 have the frequency characteristic correction function, it is possible to transmit a broadband voice signal. As such, the exemplary embodiments successfully improve speech quality.

An alternative embodiment of a speech communication system according to the invention will be described below. The system configuration described with reference to fig. 1 is equally applicable to alternative embodiments. This alternative embodiment is the same as the previous embodiment except that the transmitter F characteristic corrector circuit 31 and the receiver F characteristic corrector circuit 42 are included in each of the voice communication apparatuses 10 and 20.

Fig. 7 shows the structure of the transmitter F characteristic corrector circuit 31 included in the alternative embodiment. In an alternative embodiment, the receiver F characteristic corrector circuit 42 has the same structure as the transmitter F characteristic corrector circuit 31, and therefore it is not shown in fig. 7 and will not be specifically described.

As shown in fig. 7, the transmitter F characteristic corrector circuit 31 includes a plurality of correction filters, for example, three correction filters 31-1, 31-2, and 31-3 in the exemplary embodiment, and a switch 31S for selecting one of the correction filters 31-1 to 31-3. The correction filters 31-1, 31-2, and 31-3 have specific correction frequency characteristics shown in fig. 8A, 8B, and 8C, respectively, one of which is matched to the transmitter characteristic of the associated telephone set 11 or 12.

The switch 31S is adapted to select one of the correction filters 31-1 to 31-3 in response to a selection signal input from the control circuit of the device 11 or 12 into the transmitter F characteristic corrector circuit 31. As shown, a switch 31S may be provided at the input of the correction filters 31-1 to 31-3, and alternatively, the switch may be provided at the output of the correction filters 31-1 to 31-3. Further, alternatively, in addition to the switch 31S, another switch similar to the switch 31S may be provided at the output terminals of the correction filters 31-1 to 31-3, if necessary.

For example, the selection signal 35 for the switch 31S may be input by a user or engineer at the installation site, or may be automatically generated by the control circuit of the apparatus 10 or 20. The selection signal 35 may also be obtained from an external device, such as a server on the IP network 2 in fig. 1. More specifically, if data indicating the relationship between the type of telephone set 10 or 20 and the correction frequency characteristic is stored in a server of the IP network 2, not shown, the selection signal 31 can be acquired from the server by, for example, inputting the type of telephone set 11 or 12 with buttons arranged on the telephone set.

For example, when the voice communication apparatus 10 or 20 is connected to the telephone set 11 or 12, respectively, the user of the apparatus 10 or 20 or an engineer in charge of installation may perform actual communication measurement and then set an optimal one of the correction filters 31-1 to 31-3 of the apparatus 10 or 20, thereby selecting an optimal correction filter.

The operation of this alternative embodiment is the same as the operation of the previous embodiment after one of the correction filters 31-1 to 31-3 is selected, and therefore, in order to avoid redundancy, it is not specifically described here.

With the above-described structure, the alternative embodiment not only achieves the same advantages as the foregoing embodiment, but also allows selection of an optimum correction frequency characteristic for a specified type of telephone set, thereby further improving communication quality.

In the following, a further alternative embodiment of the speech communication system according to the invention will be described. The system configuration described with reference to fig. 1 is equally applicable to this alternative embodiment. Fig. 9 shows circuitry unique to each of the voice communication devices 10 and 20 included in this alternative embodiment. In fig. 9, the same structural parts and components as those shown in fig. 3 are denoted by the same reference numerals.

As shown in fig. 9, one embodiment of the voice communication apparatus 10 further includes a transmitter F characteristic corrector circuit 31, a voice signal-to-IP packet converter circuit 32, an IP packet-to-voice signal converter circuit 41, and a receiver F characteristic corrector circuit 42 interconnected in the manner shown. Although an embodiment of one of the voice communication apparatuses 10 is described here, it goes without saying that the same structure is equally applicable to the other voice communication apparatuses 20. In the exemplary embodiment, device 10 also includes four switches 51A-51D, FFT (fast Fourier transform) circuits or similar frequency analyzer 52, white noise generator 53, and mode controller 54. It should be noted that the transmitter and receiver F

characteristic corrector circuits

31 and 42 in the exemplary embodiment are responsive to the control signals 37 and 39, respectively, generated by the FFT circuit 52 to change their correction frequency characteristics.

For this exemplary embodiment, two different modes of operation may be used, namely a normal mode and an F characteristic setting mode. The F characteristic setting mode for setting the correction frequency characteristic can be selected by responding to automatic detection of initial connection of the telephone set 11 having the voice communication apparatus 10, for example. In the F characteristic setting mode, the mode controller 54 with the symbolically shown different control connections 61 causes different sub-parts of the apparatus 11 to operate in a manner that automatically sets the correction frequency characteristics of the transmitter and receiver

characteristic corrector circuits

31 and 42.

The switches 51A to 51D are also configured to establish a specific signal path for each of the normal mode and the F characteristic setting mode.

The frequency analyzer 52 includes, for example, an FFT circuit, which functions in the F characteristic setting mode. The frequency analyzer 52 is adapted to detect the frequency characteristics of a signal input from the telephone set 11 connected to the voice communication apparatus 10. The white noise generator 53, which also functions in the F characteristic setting mode, is adapted to generate white noise over the entire voice band.

For example, as shown in fig. 1, in operation, the voice communication apparatus 10 and the telephone set 11 are interconnected and in the F characteristic setting mode. When the F characteristic setting mode is selected, the mode controller 54 first connects all the switches 51A to 51D to its terminal a, and then causes the frequency analyzer 52 to start operating. Under such a condition, a signal representing the background noise acquired by the microphone 11S of the telephone set 11 and reflecting the transmitter characteristic of the telephone set body 11B is input to the frequency analyzer 52. In the exemplary embodiment, it is assumed that the background noise is white noise. In response, the frequency analyzer 52 determines the transmitter characteristic of the telephone set 11, and then causes the transmitter F characteristic corrector circuit 31 to select a correction frequency characteristic matching the transmitter characteristic thus determined.

For example, in an application in which the transmitter F characteristic corrector 31 has the structure shown in fig. 7, when the frequency analyzer 52 detects the transmitter characteristic so as not to greatly attenuate the low frequency part of 300Hz or less and including 300Hz or the high frequency part of 3,400Hz or more and including 3,400Hz, the frequency analyzer 52 causes the transmitter F characteristic corrector circuit 31 to select the correction filter 31-3 in fig. 7. On the other hand, in applications where a digital field capable of changing those frequency-based characteristics is applied to transmitter F corrector circuit 31, frequency analyzer 52 will cause transmitter F characteristic corrector circuit 31 to select an F characteristic that achieves the inverse of the measured transmitter characteristic.

Subsequently, the mode controller 54 connects the

switches

51A and 51B to the terminal B, connects the switch 51C to the terminal a, and connects the switch 51D to the terminal C, and then causes the frequency analyzer 52 and the white noise generator 53 to start operating. The white noise generator 53 generates white noise. The white noise thus generated is affected by the receiver characteristics of the telephone body 11B and then output as sound from the speaker 11R. The resulting sound is acquired by the microphone 11S and is affected by the transmitter characteristics of the telephone set main body 11B, and then, the sound is input to the frequency analyzer 52 via the transmitter F characteristic corrector circuit 31.

As described earlier, the transmitter F characteristic corrector circuit 31 is set so as to restore the band component limited in advance by the transmitter characteristic. Therefore, it can be reliably considered here that the signal input to the frequency analyzer reflects only the receiver characteristic of the telephone set 11. The frequency analyzer 52 determines the receiver characteristic of the telephone set 11 and then causes the receiver F characteristic corrector 42 to select a correction frequency characteristic matching the receiver characteristic.

Through the above-described procedure, the mode controller 54 connects all the switches 51A to 51D to its terminal b, thereby establishing the normal mode. It goes without saying that the voice communication apparatus embodiment applied to the other voice communication apparatus 20 operates in the same manner as described above.

As described above, the exemplary embodiment measures the transmitter and receiver characteristics of the telephone set 11 or 12 connected to the voice communication apparatus 10 or 20, respectively, and then selects an appropriate correction frequency characteristic. It follows that a specific correction frequency characteristic can be set for each telephone set 11 or 12, thereby further improving the communication quality. Of course, the exemplary embodiments also achieve the same advantages as the foregoing embodiments.

Another alternative embodiment of a voice communication system according to the present invention will be described hereinafter with reference to fig. 10. This embodiment is the same as the embodiment shown in fig. 9 except as follows. In fig. 10, the same parts and components as those of the structure shown in fig. 9 are denoted by the same reference numerals, and are not specifically described here in order to avoid redundancy. Briefly, when the transmitter and receiver characteristics of the telephone set 11 or 12 are similar to each other, this embodiment causes the voice communication apparatus 10 or 20 to operate in a different manner from the apparatus 10 or 20 in the F characteristic setting mode in the embodiment of fig. 9.

As can be seen from fig. 10, the switch 51D and the white noise generator 53 are not present in the voice communication apparatus 10. Fig. 10 shows only a voice communication apparatus applied to the voice communication apparatus 10. The same structure is also applicable to the voice communication apparatus 20. When the F characteristic setting mode is selected, the mode controller 54 connects the

switches

51A, 51B, and 51C to the terminal a, and then causes the frequency analyzer 52 to start operating.

In accordance with the above conditions, the microphone 11S of the telephone set 11 generates a signal representing the background noise thus acquired. Also, in the exemplary embodiment, it is assumed that the background noise is white noise. Therefore, a signal derived from the background noise and reflecting the transmitter characteristics of the telephone set body 11B is input to the frequency analyzer 52. In response, the frequency analyzer 52 determines the transmitter characteristic of the telephone set 11, and then causes the transmitter and receiver F

characteristic corrector circuits

31 and 42 to select the corresponding correction frequency characteristic matching the transmitter characteristic.

Through the above process, the mode controller 54 connects all the

switches

51A, 51B and 51C to its terminal B, and then establishes the normal mode. It goes without saying that the exemplary embodiment of the voice communication apparatus applied to the other voice communication apparatus 20 operates in the same manner as described above.

With the above-described structure, the present exemplary embodiment achieves the same advantages as the embodiment shown in fig. 9.

Another alternative embodiment of a voice communication system according to the present invention will now be described with reference to fig. 11. The present exemplary embodiment is similar to the embodiment shown in fig. 9 except for the following points. For this embodiment, the same structural parts and components are denoted by the same reference numerals, and are not specifically described herein in order to avoid redundancy. Only one voice communication apparatus 10 is shown in fig. 11. However, as described above, it is needless to say that the other voice communication apparatus 20 may have the same structure as the apparatus 10.

As shown in fig. 11, the voice communication apparatus 10 in the present exemplary embodiment is mainly constituted by an apparatus main body 10A and an accessory 10B for measuring F frequency characteristics. Wherein the accessory 10B is configured to operate only in the F characteristic setting mode, and is adapted to be manually coupled to the apparatus main body 10A by, for example, an engineer. Alternatively, the accessory 10B is also adapted to be fixedly coupled to and surrounded by a casing of the apparatus main body 10A, not shown, in which case the installer takes out the accessory 10B from the casing only in the F characteristic setting mode, for example, to operate it.

The accessory 10B includes a white noise generator 53, a speaker 55, a microphone 56, and a switch 57A interconnected in the manner shown. On the other hand, the apparatus body 10A includes a frequency analyzer 52, a mode controller 54, and switches 57B to 57E operatively assigned to the F characteristic setting mode and interconnected in the illustrated manner.

In operation, the engineer will position the accessory 10B so that the speaker 55 and the microphone 56 face the microphone 11S and the speaker 11R, respectively, of the handset 13 of the telephone set 11 before selecting the F characteristic setting mode. For this purpose, it is preferable to surround the accessory 10B with a casing, not shown, whose contour or shape is configured so that the speaker 55 and the microphone 56 naturally face the microphone 11S and the speaker 11R, respectively, when the handset 13 is placed thereon by hand.

When the F characteristic setting mode is selected, the mode controller 54 first connects the

switches

57A and 57B to the terminals a and B thereof, respectively. The controller 54 also turns off the switch 57C, i.e., connects it to neither terminal a nor terminal b. In addition, the controller 54 also connects the switch 57D to the terminal a thereof and turns off the switch 57E. Subsequently, the mode controller 54 causes the white noise generator 53 and the frequency analyzer 52 to start operating.

The white noise generator 53 in turn generates white noise. The white noise thus generated is converted by the speaker 55 into sound, which is in turn output from the speaker 55 and then picked up by the microphone 11S of the telephone set 11 connected to the voice communication apparatus 10. As a result, a signal reflecting the transmitter characteristic of the telephone set body 11B is input to the frequency analyzer 52. In response, the frequency analyzer 52 determines the transmitter characteristic of the telephone set 11, and then causes the transmitter F characteristic corrector circuit 31 to select a correction frequency characteristic matching the transmitter characteristic.

Subsequently, the mode controller 54 connects the switch 57A to its terminal B, turns off the switch 51B, i.e., connects it to neither terminal a nor terminal B, and also connects the switch 51C to its corresponding terminal B, and turns on the switch 57E. Then, the mode controller 54 causes the white noise generator 53 and the frequency analyzer 52 to start operating. The white noise generated from the white noise generator 53, which is affected by the receiver characteristics of the telephone set body 11B, is output via the speaker 11R and picked up by the microphone 56, and then delivered in the form of a signal to the frequency analyzer 52.

Although the signal thus input to the frequency analyzer 52 is derived from white noise, the signal reflects only the receiver characteristic of the telephone set 11. The frequency analyzer 52 determines the receiver characteristic of the telephone set 11 and causes the receiver F characteristic corrector circuit 42 to select a correction frequency characteristic matching the receiver characteristic.

Through the above-described procedure, the mode controller 54 turns off the switch 57A, i.e., connects it to neither the terminal a nor the terminal B, and also turns off the

switches

57B and 57C to its terminal a, and turns off the switch 57D, i.e., connects it to neither the terminal a nor the terminal B, and also turns off the switch 57E, thereby restoring the normal mode. It goes without saying that the voice communication apparatus embodiment applied to the other voice communication apparatus 20 also operates in the same manner as described above.

As described above, the exemplary embodiment measures the transmitter and receiver characteristics by using white noise generated by the white noise generator 53, thereby selecting an appropriate correction frequency characteristic. This will further improve the communication quality. Of course, the exemplary embodiment also achieves the same advantages as the embodiment shown in fig. 9.

In the described and illustrated embodiment, the voice communication apparatus is provided with a function of correcting the frequency characteristics in accordance with the transmitter and receiver characteristics of the telephone set, and a function of communicating with the IP network. Alternatively, the voice communication apparatus may have only the frequency characteristic correction function. Further, the voice communication apparatus may be implemented as an apparatus having any other function, such as a gateway apparatus capable of selectively connecting a telephone set to a conventional public switched telephone network or an IP network. In this case, the circuit unique to the present invention may be configured so as to operate only when the telephone set is connected to the IP network.

Although the voice communication device is shown and described herein as being separate from the telephone, the former may be embedded within the latter. By performing this processing, a high communication quality usable in connection with broadband communication can be ensured without changing the conventional basic design of the telephone set.

The transmitter F characteristic corrector circuit is also configured in the exemplary embodiment so that the frequency characteristic after correction is flat over the entire voice band. The receiver F characteristic corrector circuit is also configured so that the signal corrected after being affected by the receiver characteristic is flat over the entire voice band. Alternatively, the transmitter F characteristic corrector circuit may be configured so that the frequency characteristic is a predetermined or expected frequency characteristic after being corrected, and the receiver F characteristic corrector circuit may be configured so that the signal has a predetermined frequency characteristic after being affected by the receiver characteristic. In this case, the expected frequency characteristics do not necessarily completely correspond to each other. This desired frequency characteristic can further improve the communication quality maintained over the wideband transmission path than when the quality is affected only by the transmitter and receiver characteristics.

In summary, it should be understood that the present invention provides a voice communication apparatus and a voice communication system capable of ensuring high voice quality even when an existing telephone set uses, for example, a broadband transmission path.

The disclosures of Japanese patent applications 2002-379082 and 2003-071826, filed 12/27/2002 and 3/17/2003, respectively, including the description, claims, drawings and abstract therein, are hereby incorporated by reference in their entirety.

Although the present invention is described herein with reference to particular embodiments, the present invention is not limited to these embodiments. It is to be understood that one of ordinary skill in the art may change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

1. A voice communication apparatus interposed between a telephone set and a broadband transmission path having a communication band wider than a voice band limited by a transmitter characteristic and a receiver characteristic of the telephone set, comprising:

a transmitter frequency characteristic corrector circuit which has a first correction frequency characteristic and corrects a frequency characteristic of a signal input from the telephone set; and

a receiver frequency characteristic corrector circuit which has a second correction frequency characteristic and corrects the frequency characteristic of a signal input to the telephone set;

wherein,

the first correction frequency characteristic makes a synthesized frequency characteristic of the transmitter characteristic and the first correction frequency characteristic flat in a communication band of the broadband communication path;

the second correction frequency characteristic makes the composite frequency component of the receiver characteristic and the second correction frequency characteristic flat in the communication band of the broadband communication path.

2. The apparatus according to claim 1, wherein the first correction frequency characteristic and the second correction frequency characteristic are variable.

3. The apparatus according to claim 2, further comprising a correction frequency characteristic setting circuit that measures a transmitter characteristic and a receiver characteristic of the telephone set, and sets the first correction frequency characteristic and the second correction frequency characteristic based on a result of the measurement.

4. The apparatus according to claim 3, wherein said correction frequency characteristic setting circuit uses the measured transmitter characteristic to assume the measured transmitter characteristic as a receiver characteristic of the telephone set.

5. The apparatus according to claim 3, wherein the correction frequency characteristic setting circuit comprises:

a white noise generator for generating white noise;

a transmitter characteristic measurement circuit for outputting white noise in the form of sound and processing a signal of the white noise acquired by the microphone to convert the acquired white noise to measure a transmitter characteristic; and

a receiver characteristic measuring circuit for outputting white noise generated by the white noise generator from the speaker and processing the output white noise to measure a receiver characteristic;

the correction frequency characteristic setting circuit sets a first correction frequency characteristic and a second correction frequency characteristic in accordance with the measured transmitter characteristic and receiver characteristic, respectively.

6. A voice communication system for connecting two telephone sets via a broadband communication path having a communication band wider than a voice band limited by a transmitter characteristic and a receiver characteristic of each of the two telephone sets, wherein each of the two telephone sets is connected to the broadband communication path via a voice communication device, the voice communication device comprising:

wherein,

7. The system of claim 6, wherein the first correction frequency characteristic and the second correction frequency characteristic are variable.

8. The system according to claim 7, wherein the apparatus further comprises a correction frequency characteristic setting circuit that measures a transmitter characteristic and a receiver characteristic of the telephone set, and sets the first correction frequency characteristic and the second correction frequency characteristic based on the measurement result.

9. The system according to claim 8, wherein the correction frequency characteristic setting circuit uses the measured transmitter characteristic to assume the measured transmitter characteristic as a receiver characteristic of the telephone set.

10. The system according to claim 8, wherein the correction frequency characteristic setting circuit comprises:

a white noise generator for generating white noise;