Device for recovering missing frequency components

• US 7,539,613 B2
• Filed: 02/10/2004
• Issued: 05/26/2009
• Est. Priority Date: 02/14/2003
• Status: Expired due to Fees

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Takada, Masashi
• Primary Examiner(s): Lerner; Martin
• Application Number:
  US10/545,435
• Publication Number:
  US 20070168185A1
• Time in Patent Office: 1,932 Days
• Field of Search: 704/203, 704/205, 704/206, 704/208, 704/214, 704/225, 381/94.1, 381/94.2, 381/94.3, 330/278, 330/279, 455/20, 455/118
• US Class Current: 704/205
• CPC Class Codes: G10L 21/038 using band spreading techniques

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

1. A band recovering device for recovering frequency components lying in a frequency band lost due to band-limitation of a sound signal, comprising:

a peak-limiting amplifier configured to amplify an input narrow-band voice signal while preventing a resulting amplified voice signal from exceeding a predetermined maximum amplitude;

a peak-limitation detector configured to detect whether or not a level of the amplified voice signal output from said peak-limiting amplifier is substantially coincident with the maximum amplitude;

an amplification controller configured to increase at least either one of an amplification factor and an amount of amplification of said peak-limiting amplifier until the level of the amplified voice signal output from said peak-limitation detector is substantially coincident with the maximum amplitude; and

a band recovering circuit configured to use a voice signal component of the amplified voice signal output from said peak-limiting amplifier and the input narrow-band voice signal to produce a band-recovered voice signal including the frequency components lying in the frequency band lost, the voice signal component being in frequency higher than the input narrow-band voice signal.

2. The device in accordance with claim 1, further comprising a voice detector configured to detect at least a voiced sound signal on the basis of the input narrow-band voice signal, wherein said amplification controller increases at least either one of the amplification factor and the amount of amplification when said voice detector is detecting at least a voiced sound signal.

3. The device in accordance with claim 2, further comprising a frequency shifter configured to shift frequency components of the input narrow-band voice 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 voice signal, and wherein said frequency shifter shifts the frequency components of the input narrow-band voice signal toward the frequency band to be recovered only when said voice detector is detecting an unvoiced sound signal.

4. The device in accordance with claim 1, further comprising a frequency shifter configured to shift frequency components of the input narrow-band voice 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 voice signal;

wherein said frequency shifter shifts the frequency components of the input narrow-band voice signal toward the frequency band to be recovered when said voice detector is detecting an unvoiced sound signal.

5. The device in accordance with claim 1, wherein said band recovering circuit comprises an amplitude adjusting section configured to adjust an amplitude of the amplified voice signal output from said peak-limiting amplifier for outputting an adjusted signal, and a signal generating section configured to combine said adjusted signal with the input narrow-band voice signal in a preselected ratio for thereby generating the band-recovered voice signal.

6. The device in accordance with claim 5, wherein said amplitude adjusting section comprises a band-pass filter configured to pass the voice signal component.

7. The device in accordance with claim 5, wherein said amplitude adjusting section comprises a characteristic correcting filter configured to pass the voice signal component while adjusting amplitudes of said frequency components in accordance with said frequency band to be recovered.

8. 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 said band recovering device comprises:

a peak-limiting amplifier configured to amplify an input narrow-band voice signal while preventing a resulting amplified voice signal from exceeding a predetermined maximum amplitude;

a peak-limitation detector configured to detect whether or not a level of the amplified voice signal output from said peak-limiting amplifier is substantially coincident with the maximum amplitude;

an amplification controller configured to increase at least either one of an amplification factor and an amount of amplification of said peak-limiting amplifier until the level of the amplified voice signal output from said peak-limitation detector is substantially coincident with the maximum amplitude; and

a band recovering circuit configured to use a voice signal component of the amplified voice signal output from said peak-limiting amplifier and the input narrow-band voice signal to produce a band-recovered voice signal including the frequency components lying in the frequency band lost, the voice signal component being in frequency higher than the input narrow-band voice signal.