Arousal-level determining apparatus and arousal-level determining method

A non-transitory computer-readable recording medium having stored therein an arousal-level determining program causing a computer to execute a process comprising:

• receiving heartbeat signals for a subject;
• generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject's heartbeats;
• applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;
• identifying as a feature point a peak in the calculated spectral densities based on the detected peaks;
• and
• determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.

An arousal-level determining method by a computer, the arousal-level determining method comprising:

• receiving heartbeat signals for a subject;
• generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject's heartbeats;
• applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;
• identifying as a feature point a peak in the calculated spectral densities based on the detected peaks;
• and
• determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.

An arousal-level determining apparatus comprising:

• a processor;
• and
• a memory, wherein the processor executes a process comprising:
• receiving heartbeat signals for a subject;
• generating heartbeat-interval variation data, which indicates changes in heartbeat intervals, on a basis of the heartbeat signals indicating the subject's heartbeats;
• storing the heartbeat-interval variation data in the memory;
• applying a plurality of times a band-pass filter, which allows passage of a frequency band of a certain range of frequencies, to the heartbeat-interval variation data in the memory, the frequency band being changed for each of the plurality of times, and calculating spectral densities with respect to each frequency band, by overlapping a range of frequencies within a first frequency band of the band-pass filter with a second frequency band of the band-pass filter that is nearest to the first frequency band, to detect peaks respectively of the calculated spectral densities;
• identifying as a feature point a peak in the calculated spectral densities based on the detected peaks;
• and
• determining the arousal level of the subject on a basis of a spectral density and a frequency of the identified feature point, the arousal level inversely indicating a degree of sleepiness of the subject.