# US 2014/0207443 A1 · Audio signal restoration device and audio signal restoration method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0207443 A1 - Document ID: US20140207443A1 - Status: Published application - Kind: A1 - Application number: 14/237,623 - Filed: 2011-12-27 - Published: 2014-07-24 - Earliest claimed: 2011-12-27 - Assignees: Mitsubishi Electric Corporation - Inventors: Kosuke Hosoya; Satoru Furuta; Tadashi Yamaura - Web page: https://patentgrep.com/patent/US20140207443A1 ## CPC - G10L 19/012: Comfort noise or silence coding - G10L 21/0208: Noise filtering - G10L 21/0388: Details of processing therefor - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract A sound source generating unit 101 generates from a narrowband audio signal not passing through noise suppression a sound source signal including a fine structure of a band to be restored. On the other hand, a noise suppressing unit 102 performs noise suppression of the narrowband audio signal and a spectral envelope estimating unit 103 estimates an spectral envelope of the band to be restored. A signal synthesizing unit 104 generates a pseudo-audio signal by combining the sound source signal and the spectral envelope, and the band-pass filter unit 105 passes the pseudo-audio signal of the band to be restored, and the signal addition unit 106 generates a broadband audio restoration signal by adding the pseudo-audio signal of the band to be restored to the narrowband audio signal. ## Claims ### Claim 1 An audio signal restoration device comprising: a sound source generating unit that generates from an audio signal of a first frequency band a sound source signal of a second frequency band including the first frequency band; a noise suppressing unit that suppresses a noise component included in the audio signal of the first frequency band; a spectral envelope estimating unit that estimates a spectral envelope of the second frequency band from the audio signal of the first frequency band passing through noise suppression by the noise suppressing unit; and a signal synthesizing unit that generates an audio signal of the second frequency band by combining the sound source signal of the second frequency band the sound source generating unit generates and the spectral envelope of the second frequency band the spectral envelope estimating unit estimates. ### Claim 2 (depends on 1) The audio signal restoration device according to claim 1, further comprising: a weak noise suppressing unit that suppresses the noise component included in the audio signal of the first frequency band while limiting the noise suppression amount within a prescribed upper limit, wherein the sound source generating unit generates the sound source signal of the second frequency band from the audio signal of the first frequency band passing through the noise suppression by the weak noise suppressing unit. ### Claim 3 (depends on 1) The audio signal restoration device according to claim 1, wherein the spectral envelope estimating unit estimates, as the spectral envelope, mean values of an amplitude spectrum of the second frequency band from mean values of the amplitude spectrum obtained from the audio signal of the first frequency band passing through the noise suppression by the noise suppressing unit. ### Claim 4 (depends on 1) The audio signal restoration device according to claim 1, further comprising: a first band-pass filter unit that extracts an audio signal of a third frequency band within the second frequency band from the audio signal of the second frequency band passing through synthesis of the signal synthesizing unit; and a signal addition unit that adds the audio signal of the third frequency band extracted by the first band-pass filter unit and the audio signal of the first frequency band. ### Claim 5 (depends on 4) The audio signal restoration device according to claim 4, further comprising: a second band-pass filter unit that extracts from the audio signal of the first frequency band an audio signal of a fourth frequency band that is within the first frequency band and does not include the third frequency band, wherein the signal addition unit adds the audio signal of the third frequency band extracted by the first band-pass filter unit and the audio signal of the fourth frequency band extracted by the second band-pass filter unit. ### Claim 6 (depends on 4) The audio signal restoration device according to claim 4, wherein the signal addition unit adds the audio signal of the third frequency band extracted by the first band-pass filter unit and the audio signal of the first frequency band passing through the noise suppression by the noise suppressing unit. ### Claim 7 (depends on 4) The audio signal restoration device according to claim 4, further comprising: a spectrum shaping unit that shapes the spectrum of the audio signal the signal addition unit generates. ### Claim 8 An audio signal restoration method comprising: a sound source generating step that generates from an audio signal of a first frequency band a sound source signal of a second frequency band including the first frequency band; a noise suppressing step that suppresses a noise component included in the audio signal of the first frequency band; a spectral envelope estimating step that estimates a spectral envelope of the second frequency band from the audio signal of the first frequency band passing through noise suppression by the noise suppressing step; and a signal synthesizing step that generates an audio signal of the second frequency band by combining the sound source signal of the second frequency band the sound source generating step generates and the spectral envelope of the second frequency band the spectral envelope estimating step estimates.