# US 9,437,179 B2 · Reverberation suppression device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,437,179 B2 - Document ID: US9437179B2 - Status: Granted - Kind: B2 - Application number: 14/238,478 - Filed: 2012-01-30 - Published: 2014-07-10 - Granted: 2016-09-06 - Earliest claimed: 2012-01-30 - Assignees: Mitsubishi Electric Corporation - Applicants: Takashi Mikami; Atsuyoshi Yano - Inventors: Takashi Mikami; Atsuyoshi Yano - Web page: https://patentgrep.com/patent/US9437179B2 ## CPC - G10K 11/002: {Devices for damping, suppressing, obstructing or conducting sound in acoustic devices (G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002)} - H04M 9/082: {using echo cancellers (echo cancellers per se H04B3/23)} - H04R 3/02: for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)} - G10L 2021/02082: {the noise being echo, reverberation of the speech} - H04R 2499/13: Acoustic transducers and sound field adaptation in vehicles - H04S 7/00: Indicating arrangements; Control arrangements, e.g. balance control - H04S 2420/05: Application of the precedence or Haas effect, i.e. the effect of first wavefront, in order to improve sound-source localisation - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H04S: STEREOPHONIC SYSTEMS ## Abstract A reverberation suppression device comprises: an echo canceller that removes an echo component included in an input signal; a howling suppressor that detects occurrence of howling based on a frequency characteristic of the input signal from which the echo component has been removed and attenuates a frequency level of a component of the detected howling; and an initial sound suppressor that detects a sound section of the input signal in which the frequency level of the howling component has been attenuated and suppresses a signal value at a sound start portion of the detected sound section. ## Claims ### Claim 1 A reverberation suppression device comprising: an input terminal that receives an input signal, the input signal being generated from sound; circuitry that calculates a filter coefficient based on a moving average of input signals of sound and a parameter, and suppresses a signal value of the input signal using the calculated filter coefficient to generate an output signal; and an output terminal that outputs the output signal, wherein the parameter is set so that the filter coefficient is at least 1 for a sound section of the input signal, and so that the filter coefficient is less than 1 for a soundless section of the input signal. ### Claim 2 (depends on 1) The reverberation suppression device according to claim 1, wherein the circuitry further: converts a signal value of the input signal on a basis of the filter coefficient; refers to the signal value of the input signal, and calculates short-time power by taking a moving average of power of signal values for a predetermined time period to smooth said power of signal values; calculates the filter coefficient by using the short-time power calculated and the parameter of the filter coefficient set; and sets an upper limit value of the filter coefficient, wherein the circuitry converts the signal value of the input signal on a basis of the filter coefficient or the upper limit value of the filter coefficient. ### Claim 3 (depends on 2) The reverberation suppression device according to claim 2, wherein the circuitry further refers to the input signal, and calculates long-time power by taking a moving average of power of signal values for a time period to smooth said power of signal values, the time period being longer than the time period used to calculate the short-time power, wherein the parameter is set on a basis of the long-time power calculated. ### Claim 4 (depends on 3) The reverberation suppression device according to claim 3, wherein the circuitry further calculates variation of the signal value of the input signal, and detects variations of signal values at a sound start portion and a sound end portion of the sound section by using a hysteresis characteristic which depends on the calculated variations, wherein the filter coefficient is calculated by using the variations of signal value at the sound start portion and the sound end portion of the sound section, the short-time power, and the parameter of the filter coefficient. ### Claim 5 (depends on 2) The reverberation suppression device according to claim 2, wherein the circuitry further calculates variation of the signal value of the input signal, and detects variations of signal values at a sound start portion and a sound end portion of the sound section by using a hysteresis characteristic which depends on the calculated variations, wherein the filter coefficient is calculated by using the variations of signal value at the sound start portion and the sound end portion of the sound section, the short-time power, and the parameter of the filter coefficient. ### Claim 6 (depends on 2) The reverberation suppression device according to claim 2, wherein the circuitry sets the upper limit value to 1. ### Claim 7 (depends on 1) The reverberation suppression device according to claim 1, wherein the circuitry further limits the filter coefficient to have an upper limit value of 1 when calculating the filter coefficient, and suppresses the signal value of the input signal by performing multiplication between the input signal and the filter coefficient. ### Claim 8 (depends on 1) The reverberation suppression device according to claim 1, wherein the circuitry is configured to calculate the filter coefficient by the following formula: p A where p denotes the moving average of the input signals, and A denotes the parameter.