# US 2013/0156205 A1 · Howling detection device, howling suppressing device and method of detecting howling > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0156205 A1 - Document ID: US20130156205A1 - Status: Published application - Kind: A1 - Application number: 13/819,778 - Filed: 2012-02-24 - Published: 2013-06-20 - Earliest claimed: 2011-03-09 - Assignees: Panasonic Corporation - Inventors: Takefumi Ura - Web page: https://patentgrep.com/patent/US20130156205A1 ## CPC - H04R 3/02: for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)} - H04R 25/453: {electronically} - 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) ## Abstract The present invention provides a howling detection device capable of detecting the occurrence of howling with a higher degree of accuracy. A howling detection device (300) is provided with a signal level calculating unit (310) calculating, from the input signal, an input signal level being the signal level of an input signal at each given time, a level fluctuation estimated value calculating unit (320) calculating, from the input signal level, a level fluctuation estimated value being a value gradually increasing or decreasing by a given amount with time, a threshold value calculating unit (330) calculating, from the level fluctuation estimated value, a level threshold value changing in accordance with the level fluctuation estimated value, and a howling determination unit (340); which determines that howling occurs in an input signal under the condition that the input signal level being higher than the level threshold value continues for a given time. ## Claims ### Claim 1 A howling detection apparatus comprising: a signal level calculation section that calculates, from an input signal, an input signal level that is a signal level of said input signal at each predetermined time; a level fluctuation estimated value calculation section that calculates a level fluctuation estimated value that is a value that gradually increases or gradually decreases by a predetermined amount from said input signal level over time; a threshold value calculation section that calculates, from said level fluctuation estimated value, a level threshold value that changes according to said level fluctuation estimated value; and a howling determination section that determines that howling has occurred in an input signal on a condition that a state in which said input signal level exceeds said level threshold value continues in excess of a predetermined time threshold value. ### Claim 2 (depends on 1) The howling detection apparatus according to claim 1, wherein said level fluctuation estimated value is one of the following: a value that gradually increases by a predetermined amount from a minimum value of said input signal level, a value that gradually decreases by a predetermined amount from a maximum value of said input signal level, or a value that gradually increases or gradually decreases by a predetermined amount from an average value of said input signal level. ### Claim 3 (depends on 2) The howling detection apparatus according to claim 2, wherein said level fluctuation estimated value is a value that is sequentially updated in accordance with a transition of said input signal level, and performs tracking in a state in which an update amount per said predetermined time is limited. ### Claim 4 (depends on 3) The howling detection apparatus according to claim 3, wherein: said update amount includes an increase amount; said level fluctuation estimated value calculation section takes a transition of a minimum value of said input signal level as said transition of said input signal level; and said threshold value calculation section takes a value obtained by multiplying said level fluctuation estimated value by a value exceeding 1, or a value obtained by adding a value exceeding 0 to said level fluctuation estimated value, as said level threshold value. ### Claim 5 (depends on 3) The howling detection apparatus according to claim 3, wherein; said update amount includes a decrease amount; said level fluctuation estimated value calculation section takes a transition of a maximum value of said input signal level as the transition of said input signal level; and said threshold value calculation section takes a value obtained by multiplying said level fluctuation estimated value by a value exceeding 0 and less than 1, or a value obtained by subtracting a value exceeding 0 from said level fluctuation estimated value, as said level threshold value. ### Claim 6 (depends on 3) The howling detection apparatus according to claim 3, wherein: said update amount includes an increase amount; said level fluctuation estimated value calculation section takes a transition of a long-term average value of said input signal level as said transition of said input signal level; and said threshold value calculation section takes a value obtained by multiplying said level fluctuation estimated value by a value greater than or equal to 1, or a value obtained by adding a value greater than or equal to 0 to said level fluctuation estimated value, as said level threshold value. ### Claim 7 (depends on 4) The howling detection apparatus according to claim 4, wherein said level fluctuation estimated value calculation section tracks said level fluctuation estimated value for said input signal level without limiting said increase amount in a rise of said input signal level. ### Claim 8 (depends on 1) The howling detection apparatus according to claim 1, further comprising: a frequency peak detection section that determines whether or not howling has occurred in said input signal based on presence or absence of a frequency peak of said input signal; and a howling comprehensive determination section that performs final determination that howling has occurred, on the condition that said howling has been determined to have occurred by both said howling determination section and said frequency peak detection section. ### Claim 9 (depends on 8) The howling detection apparatus according to claim 8, wherein said howling comprehensive determination section performs final determination that howling has occurred, on the condition that a difference between a time for which said howling determination section determines said howling to have occurred and a time for which said frequency peak detection section determines said howling to have occurred is within a predetermined range. ### Claim 10 (depends on 1) A howling suppression apparatus comprising: the howling detection apparatus according to claim 1; and a howling suppression section that performs processing to suppress said howling for said input signal when said howling detection apparatus determines that said howling has occurred. ### Claim 11 (depends on 10) The howling suppression apparatus according to claim 10, wherein said howling suppression section uses an adaptive filter corresponding to a transfer characteristic of an acoustic feedback path of said input signal. ### Claim 12 (depends on 10) The howling suppression apparatus according to claim 10, wherein said howling suppression section reduces a gain of a frequency band in which a frequency peak of said input signal occurs. ### Claim 13 A howling detection method comprising: a step of calculating, from an input signal, an input signal level that is a signal level of said input signal at each predetermined time; a step of calculating a level fluctuation estimated value that is a value that gradually increases or gradually decreases by a predetermined amount from said input signal level over time; a step of calculating, from said level fluctuation estimated value, a level threshold value that changes according to said level fluctuation estimated value; and a step of determining that howling has occurred in an input signal on a condition that a state in which said input signal level exceeds said level threshold value continues in excess of a predetermined time threshold value.