1. A noise detector for detecting noise contained in an input signal, the noise detector comprising: a noise discrimination portion having a plurality of discrimination portions to which the input signal is input, and a noise determination portion determining the noise based on individual discrimination results of the plurality of discrimination portions, wherein the noise discrimination portion comprises at least two of a frequency component discrimination portion discriminating the presence or absence of the noise based on a frequency component of the input signal, a temporal change discrimination portion discriminating the presence or absence of the noise based on a temporal change of the input signal, and a high-frequency component discrimination portion discriminating the presence or absence of the noise based on a high-frequency component of the input signal, and the noise determination portion determines the noise based on individual discrimination results of the plurality of discrimination portions.