# US 2008/0189102 A1 · Device for recovering missing frequency components

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2008/0189102 A1
- Document ID: US20080189102A1
- Status: Published application
- Kind: A1
- Application number: 12/073,986
- Filed: 2008-03-12
- Published: 2008-08-07
- Earliest claimed: 2003-02-14
- Assignees: Oki Electric Industry Co., Ltd.
- Inventors: Masashi Takada
- Web page: https://patentgrep.com/patent/US20080189102A1

## CPC

- G10L 21/038: using band spreading techniques
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A band recovering device recovers frequency components lying in a frequency band lost due to band-limitation of a sound signal. The device includes a peak-limiting amplifier for amplifying an input narrow-band signal while preventing the resulting amplified signal from exceeding a maximum amplitude. A peak-limitation detector detects the level of the amplified signal output. An amplification controller increases the amplification factor and/or the amount of amplification of the peak-limiting amplifier in accordance with the level of the amplified signal. A band recovering circuit generates, based on the amplified signal output from the peak-limiting amplifier and input narrow-band signal, a band-recovered signal including the frequency components lying in the missing band.

## Claims

### Claim at position 1

1-8. (canceled)

### Claim 9

A band recovering device for recovering frequency components lying in a frequency band lost due to band-limitation of a sound signal, comprising:
an amplitude limiter configured to limit an upper limit of a signal value of the input narrow-band signal;
a detector configured to detect a level of the signal value of the input narrow-band signal;
an amplitude-limit controller configured to decrease the upper limit in accordance with an output of said detector; and
a band recovering circuit configured to generate, based on a signal output from said amplitude limiter and the input narrow-band signal, a band-recovered signal including the frequency components lying in the frequency band lost.

### Claim 10 (depends on 9)

The device in accordance with claim 9, further comprising a voice detector configured to detect at least a voiced sound signal on the basis of the input narrow-band signal,
wherein said amplitude-limit controller reduces the upper limit when said voice detector is detecting at least a voiced sound signal.

### Claim 11 (depends on 10)

The device in accordance with claim 10, further comprising a frequency shifter configured to shift frequency components of the input narrow-band signal toward the frequency band to be recovered,
wherein said voice detector detects at least an unvoiced sound signal on the basis of the input narrow-band signal, and
wherein said frequency shifter shifts the frequency components of the input narrow-band signal toward the frequency band to be recovered only when said voice detector is detecting an unvoiced sound signal.

### Claim 12 (depends on 9)

The device in accordance with claim 9, further comprising a frequency shifter configured to shift frequency components of the input narrow-band signal toward the frequency band to be recovered, and a voice detector configured to detect at least an unvoiced sound signal on the basis of the input narrow-band signal;
wherein said frequency shifter shifts the frequency components of the input narrow-band signal toward the frequency band to be recovered when said voice detector is detecting an unvoiced sound signal.

### Claim 13 (depends on 9)

The device in accordance with claim 9, wherein said band recovering circuit comprises an amplitude adjusting section configured to adjust an amplitude of a signal output from said amplitude limiter for thereby outputting an adjusted signal, and a signal generating section configured to combine said adjusted signal with the input narrow-band signal in a preselected ratio for thereby generating the band-recovered signal.

### Claim 14 (depends on 13)

The device in accordance with claim 13, wherein said amplitude adjusting section comprises a band-pass filter configured to pass only frequency components of a frequency band necessary for recovery.

### Claim 15 (depends on 13)

The device in accordance with claim 13, wherein said amplitude adjusting section comprises a characteristic correcting filter configured to pass frequency components of a frequency band necessary for recovery while adjusting amplitudes of said frequency components in accordance with said frequency band.

### Claim 16

A telephone set comprising a band recovering device for recovering frequency components lying in a frequency band lost due to band-limitation of a sound signal, wherein a band recovering device comprises:
an amplitude limiter configured to limit an upper limit of a signal value of the input narrow-band signal;
a detector configured to detect a level of the signal value of the input narrow-band signal;
an amplitude-limit controller configured to decrease the upper limit in accordance with an output of said detector; and
a band recovering circuit configured to generate, based on a signal output from said amplitude limiter and the input narrow-band signal, a band-recovered signal including the frequency components lying in the frequency band lost.