A noise monitoring apparatus adapted to determine time points when there is at least one source change in a monitoring environment where at least one single event noise and at least one semi-stationary noise occur, characterized in that it comprises: a microphone unit adapted to sense noise in the monitoring environment in a predetermined time range; a detecting means (102, S100) adapted to detect and discriminate at least a single event noise and a semi-stationary noise in the noise sensed by the microphone unit in the predetermined time range, each detected noise occurring during a detected time section; a characteristic amount calculating means (106, 8200) adapted to calculate, per unit time, as a characteristic amount indicating a change in an arrival direction of each of the noises detected by the detecting means in the predetermined time range, a value of at least one of o an arrival direction movement amount indicating a change amount in the arrival direction of the noise, o a standard deviation of an elevation angle of the noise, from a horizontal plane set in the monitoring environment, and o a standard deviation of an angle of direction of the noise, relative to a reference azimuth set in the monitoring environment; a smoothing means (106, S300) adapted to smooth the characteristic amount having plural values in the predetermined time range and calculated by the characteristic amount calculating means; an extracting means (106, 8400) adapted to extract at least one candidate point, said candidate point being a time point when a fluctuation of the characteristic amount smoothed by the smoothing means is detected outside the time sections of single event noises detected by the detecting means; and an excluding means (106, 8500, 8600) adapted to exclude from among candidate points extracted by the extracting means, any candidate point existing in a predetermined first time interval prior and posterior to a time section of a single event noise and any candidate point existing in a predetermined second time interval prior and posterior to another candidate point. a microphone unit adapted to sense noise in the monitoring environment in a predetermined time range; a detecting means (102, S100) adapted to detect and discriminate at least a single event noise and a semi-stationary noise in the noise sensed by the microphone unit in the predetermined time range, each detected noise occurring during a detected time section; a characteristic amount calculating means (106, 8200) adapted to calculate, per unit time, as a characteristic amount indicating a change in an arrival direction of each of the noises detected by the detecting means in the predetermined time range, a value of at least one of o an arrival direction movement amount indicating a change amount in the arrival direction of the noise, o a standard deviation of an elevation angle of the noise, from a horizontal plane set in the monitoring environment, and o a standard deviation of an angle of direction of the noise, relative to a reference azimuth set in the monitoring environment; o an arrival direction movement amount indicating a change amount in the arrival direction of the noise, o a standard deviation of an elevation angle of the noise, from a horizontal plane set in the monitoring environment, and o a standard deviation of an angle of direction of the noise, relative to a reference azimuth set in the monitoring environment; a smoothing means (106, S300) adapted to smooth the characteristic amount having plural values in the predetermined time range and calculated by the characteristic amount calculating means; an extracting means (106, 8400) adapted to extract at least one candidate point, said candidate point being a time point when a fluctuation of the characteristic amount smoothed by the smoothing means is detected outside the time sections of single event noises detected by the detecting means; and an excluding means (106, 8500, 8600) adapted to exclude from among candidate points extracted by the extracting means, any candidate point existing in a predetermined first time interval prior and posterior to a time section of a single event noise and any candidate point existing in a predetermined second time interval prior and posterior to another candidate point.