Oki Electric Industry Co., Ltd.

Kazuyoshi Akie

Hiromi Aoyagi

Atsushi Yokoyama

Nobuyuki Yamaguchi

Masashi Takada

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.

Voice communications apparatus

A voice packet communications system which objectively evaluates the voice quality in real time. Voice packets received from a network are input into an adjustment circuit. The adjustment circuit evens out the periods of the voice packets, detects the drop-out of voice packets, and inserts substitute packets in the voice packet sequence. Furthermore, the adjustment circuit outputs the number of voice packets that have dropped out, the number of substitute packets that have been inserted, and the number of voice packets that have accumulated inside the circuit, as quality information in each monitoring period. A decoding circuit converts the voice packets adjusted by the adjustment circuit into voice information. A judgement circuit calculates an index that indicates the communications quality of the voice packets from the quality information using a specified calculation formula.

Voice packet communications system with communications quality evaluation function

A voice communication apparatus is interposed between a telephone set and a public switched telephone network (PSTN) or a broadband network which can provide a frequency bandwidth broader than a frequency bandwidth of the public switched telephone network. The apparatus selects one of the PSTN and the broadband network, from which a voice signal is input. The apparatus takes account of the selected network, frequency characteristics of the selected network and of the telephone set, and appropriately adjusts frequency characteristics of a voice signal transmitted between the telephone set and the selected network by means of transmitter and receiver band-pass filter units. As a result, both the telephone set and the counterpart communication terminal can receive a voice signal of better transmission quality.

Voice communication apparatus

A voice packet communications system which objectively evaluates the voice quality in real time. Voice packets received from a network are input into an adjustment circuit. The adjustment circuit evens out the periods of the voice packets, detects the drop-out of voice packets, and inserts substitute packets in the voice packet sequence. Furthermore, the adjustment circuit outputs the number of voice packets that have dropped out, the number of substitute packets that have been inserted, and the number of voice packets that have accumulated inside the circuit, as quality information in each monitoring period. A decoding circuit converts the voice packets adjusted by the adjustment circuit into voice information. A judgment circuit calculates an index that indicates the communications quality of the voice packets from the quality information using a specified calculation formula.

In a system in which echo transferred from a received signal to an outgoing signal is canceled by subtracting an adaptively predicted echo signal from the outgoing signal, howling is detected by detecting the effect of the predicted echo signal. The detected effect preferably depends on the magnitude or polarity of the predicted echo signal. The effect may be detected by comparing an envelope of the received signal or outgoing signal with a corresponding envelope of the residual outgoing signal left after echo cancellation. The echo attenuation on the echo path from the received signal to the outgoing signal may also be calculated, the conditions for howling detection being made more stringent as the detected echo attenuation increases. When howling is detected, it may be suppressed by attenuating the residual outgoing signal or initializing an adaptive filter that generates the predicted echo signal.

Anti-howling circuit detecting howling from effect of predicted echo signal

A quality control device which improves the quality of voice packet communication. The quality control device used for voice packet communications for transmitting voice packets through a quality non-asurance type network includes a buffer memory for temporarily storing voice packets received through the network and forming a queue of the received voice packets, a queue operating device for operating the queue in accordance with an operation control signal to be supplied, a sequence examining device for examining vocal properties of a sequence of voice information contained in a plurality of voice packets that constitute the queue stored in the buffer memory, and an operation control device for changing the operation control signal in accordance with an examination result of the sequence examining means.

Quality control device for voice packet communications

Circuitry for detecting tonal signals, each of which has a particular nature in the frequency or time domain, while distinguishing them from each other. A rough frequency analyzer roughly analyzes an input signal in an entire frequency band with lower accuracy in the frequency or time domain, thereby roughly distinguishing the tonal signals. Detectors, each of which is associated with a subband occupied by a particular target tonal signal, detect the attribute of the power variation of the target tonal signal with respect to time with higher accuracy in the direction of the frequency or time domain to thereby finely identify the target tonal signal. A controller selectively enables and disables the detectors in accordance with the results from the detectors. One of the detectors is enabled which is selected under the control of the controller.

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Saitama, Japan

Kazuyoshi Akie