Howling suppression device, hearing aid, howling suppression method, and integrated circuit

A howling suppression method for reducing a howling component included in an input signal, the howling suppression method comprising:

• generating an error signal by subtracting, from the input signal, a pseudo feedback signal which is an estimated signal of a feedback signal that is the howling component included in the input signal;
• generating a pseudo feedback signal for a next input signal by applying filtering to the error signal;
• and
• controlling an update rate of a filter coefficient for the generating of the pseudo feedback signal,
• wherein the controlling includes:
• determining whether or not a first condition that a degree of convergence of filter characteristics of the adaptive filter with respect to spatial transfer characteristics is higher than a criterion value is satisfied, the filter characteristics being determined by the filter coefficient;
• determine whether or not a second condition that the degree of convergence of the filter characteristics with respect to the spatial transfer characteristics has turned out to be higher than a predetermined period of time before is satisfied;
• and
• setting the update rate to a first rate when both the first condition and the second condition are satisfied, and setting the update rate to a second rate when at least one of the first condition or the second condition is not satisfied, the second rate being lower than the first rate, and
• in the generating of the pseudo feedback signal, the filter coefficient for the application of the filtering to the error signal is updated at the update rate set in the controlling.

An integrated circuit which reduces a howling component included in an input signal, the integrated circuit comprising:

• a subtractor which generates an error signal by subtracting, from the input signal, a pseudo feedback signal which is an estimated signal of a feedback signal that is the howling component included in the input signal;
• an adaptive filter which generates a pseudo feedback signal for a next input signal by applying filtering to the error signal;
• and
• a coefficient update control unit configured to control an update rate of a filter coefficient of the adaptive filter,
• wherein the coefficient update control unit includes:
• a convergence analysis unit configured to determine whether or not a first condition that a degree of convergence of filter characteristics of the adaptive filter with respect to spatial transfer characteristics is higher than a criterion value is satisfied, the filter characteristics being determined by the filter coefficient;
• a change amount analysis unit configured to determine whether or not a second condition that the degree of convergence of the filter characteristics with respect to the spatial transfer characteristics has turned out to be higher than a predetermined period of time before is satisfied;
• and
• an update rate control unit configured to set the update rate to a first rate when both the first condition and the second condition are satisfied, and set the update rate to a second rate when at least one of the first condition or the second condition is not satisfied, the second rate being lower than the first rate, and
• the adaptive filter updates the filter coefficient for the application of the filtering to the error signal at the update rate set by the update rate control unit.