Audio encoding apparatus and audio encoding method

An audio encoding apparatus comprising:

• a memory;
• and
• a processor coupled to the memory and the processor configured to:
• determine whether a tone is included within a portion of a frequency bandwidth near a boundary between a low-frequency that is a frequency bandwidth below a predetermined frequency of an input signal and a high-frequency that is a frequency bandwidth above the predetermined frequency of the input signal, the tone having the largest power in one of the low-frequency and the high-frequency;
• suppress the tone in one of the low-frequency and the high-frequency when determined that the tone is included within the portion of the frequency bandwidth near the boundary;
• encode a signal of the low-frequency included in the input signal to generate a low-frequency code;
• encode a signal of the high-frequency included in the input signal to generate a high-frequency code;
• and
• generate an encoded stream, based on the suppressed tone, by multiplexing the low-frequency code and the high-frequency code,
• wherein, when the tone is included within the portion of the frequency bandwidth near the boundary, shift a frequency of a lower limit in the high-frequency to a high frequency side by a predetermined frequency or shift a frequency of an upper limit in the low-frequency to a low frequency side by a predetermined frequency to exclude the tone.