An apparatus and a method for detecting the energy of a tone signal. A
pre-process unit takes absolute values of transmitted samples and outputs
the values to a delay unit for delaying the transmitted samples according
to a predetermined delay interval. An operation unit subtracts the value
calculated by multiplying the magnitudes of the samples transmitted
before and after the burst detection from the square value of the
magnitude of the sample at the time of burst detection among the delayed
transmitted samples. A detection unit detects the burst by confirming
whether peaks corresponding to the number of the samples transmitted
before the sample of the burst detection are detected by a signal of an
value input from the operation unit. Therefore, the present invention can
reduce a probability of a false alarm caused by an impulse error and
burst errors and thus perform stable burst detection.