Noise removal device and noise removal method

1. A noise removal device for removing noise included in an input signal, the noise removal device comprising:

a noise detector that detects noise in the input signal and outputs a noise detection signal;

an interpolation controller that determines a period an amount of interpolation for a noise correction processing, based on the input signal and the noise detection signal; and

a noise gate processor that performs the noise correction processing on the input signal, based on the interpolation period and the interpolation amount supplied from the interpolation controller,

wherein the interpolation controller sets a predetermined first interpolation period as the interpolation period, based on a first noise detection signal inputted from the noise detector, and redefines a second interpolation period longer the first interpolation period as the interpolation period when a second noise detection signal is detected within the first interpolation period,

wherein the interpolation controller includes:

a gate signal elongating unit that generates a noise gate signal for the first interpolation period by elongating the noise detection signal;

a noise interval detector that detects output of the second noise detection signal within the first interpolation period, and outputs a noise interval detection signal;

an interpolation amount calculator that calculates an amount of interpolation for noise correction within the first interpolation period by using a linear interpolation scheme; and

an interpolation scheme selector that selects any one of the linear interpolation scheme and a previous-value hold scheme depending on the noise interval detection signal, and the interpolation scheme selector selects the linear interpolation scheme when not receiving the noise interval detection signal, and selects the previous-value hold scheme when receiving the noise interval detection signal, and

wherein upon receipt of the noise interval detection signal, the gate signal elongating unit generates the noise gate signal for the second interpolation period by extending the first interpolation period.

2. The noise removal device according to claim 1 , wherein when the noise interval detector detects an output of a third noise detection signal within the second interpolation period and further outputs the noise interval detection signal, the gate signal elongating unit redefines a third interpolation period longer than the second interpolation period as the interpolation period.

3. The noise removal device according to claim 2 , wherein the interpolation controller further includes a counter that counts a number of the noise interval detection signals, and that outputs a redefining disabling signal when the number of counts reaches a predetermined count value, and

the gate signal elongating unit disables an operation of redefining of the interpolation period in response to the redefining disabling signal.

4. The noise removal device according to claim 1 , further comprising a level detector that detects a level of the input signal,

wherein when the detected level of the input signal is larger than a predetermined level, the noise interval detector does not output the noise interval detection signal.

5. A noise removal method of removing noise included in an input signal, the noise removal method comprising:

detecting noise in the input signal and outputting a noise detection signal;

generating a noise gate signal for a predetermined interpolation period by elongating the noise detection signal;

redefining the interpolation period and generating the noise gate signal for the redefined interpolation period when a new noise detection signal is detected while the noise gate signal is being outputted; and

performing noise correction processing on the input signal in accordance with the interpolation period and an interpolation amount determined based on the interpolation period,

wherein the noise correction processing is performed by using a linear interpolation scheme when the interpolation period is not redefined, and by using a previous-value hold scheme when the interpolation period is redefined.

6. The noise removal method according to claim 5 , wherein an operation of redefining of the interpolation period is disabled when a number of times that the interpolation period is redefined reaches a predetermined value.

7. The noise removal method according to claim 5 , wherein when a level of the input signal is higher than a predetermined level, an operation of redefining of the interpolation period is disabled.