APNEA EPISODE DETERMINATION DEVICE AND APNEA EPISODE DETERMINATION METHOD

• US 20130261485A1
• Filed: 12/03/2012
• Published: 10/03/2013
• Est. Priority Date: 03/27/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: ISHIKAWA, Chisato, Togawa, Taro, Otani, Takeshi, Suzuki, Masanao, Nishida, Asako
• Granted Patent: US 9,629,582 B2
• Time in Patent Office: Days
• US Class Current: 600/529
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise

Abstract

An apnea episode determination device includes, a processor; and a memory which stores a plurality of instructions, which when executed by the processor, cause the processor to execute, detecting a breathing segment and a midway segment from a sound signal during sleep, the breathing segment being considered to include a breathing sound, the midway segment existing in between the breathing segments; calculating an acoustic feature based on a background noise component and a signal component excluding the background noise component, which are included in the midway segment; and determining that the midway segment is an apnea episode when the acoustic feature meets a preset condition.

Claims

1. An apnea episode determination device comprising:

a processor; and

a memory which stores a plurality of instructions, which when executed by the processor, cause the processor to execute,

detecting a breathing segment and a midway segment from a sound signal during sleep, the breathing segment being considered to include a breathing sound, the midway segment existing in between the breathing segments;

calculating an acoustic feature based on a background noise component and a signal component excluding the background noise component, which are included in the midway segment; and

determining that the midway segment is an apnea episode when the acoustic feature meets a preset condition.

2. The device according to claim 1,

wherein the calculating calculates a signal-to-noise ratio in the midway segment as the acoustic feature, and

wherein the determining determines that the midway segment is an apnea episode when the signal-to-noise ratio is less than a preset threshold.

3. The device according to claim 2, further comprising:

the memory which stores a plurality of instructions, which when executed by the processor, cause the processor to further execute,

dividing the sound signal from a subject during sleep into frames, each of which has a preset time length; and

estimating power of noise included in the sound signal in each of the frames;

wherein the calculating calculates the signal-to-noise ratio in the midway segment based on the power of noise estimated by the estimating.

4. The device according to claim 3,

wherein the estimating estimates the power of noise in one frame based on the power of noise in a last frame before the one frame and a sound volume of the sound signal included in the one frame when an amount of change in the sound signal included in the one frame is less than a preset value.

5. The device according to claim 3,

wherein the estimating estimates the power of noise in one frame based on the power of noise in a last frame before the one frame and a sound volume of the sound signal included in the one frame when a ratio of the sound signal included in the one frame to the power of noise of the last frame before the one frame is less than a preset ratio.

6. The device according to claim 1,

wherein the calculating obtains a correlation between the sound signal in the midway segment and at least one of the sound signals in the breathing segments immediately before and immediately after the midway segment as the acoustic feature, and

wherein the determining determines that the midway segment is an apnea episode when the correlation is less than a preset threshold.

7. The device according to claim 6,

wherein the calculating calculates the correlation based on a difference in power spectrum between the sound signal in the midway segment and at least one of the sound signals in the breathing segments immediately before and immediately after the midway segment.

8. The device according to claim 1,

wherein the calculating includes a breathing interval calculating that obtains a time length of the midway segment, and

wherein the determining determines that the midway segment is an apnea episode when the acoustic feature meets the preset condition and the time length of the midway segment is within a preset range.

9. The device according to claim 1, further comprising;

calculating an acoustic feature of at least one of the sound signals of the breathing segments immediately before and immediately after the midway segment,

wherein the determining determines that the midway segment is an apnea episode when the acoustic feature of the sound signal in the midway segment and the acoustic feature of at least one of the sound signals in the breathing segments immediately before and immediately after the midway segment meet preset conditions.

10. The device according to claim 9,

wherein the calculating calculates the time length of at least one of the sound signals in the breathing segments immediately before and immediately after the midway segment, and

determines that the midway segment is an apnea episode when the acoustic feature of the sound signal in the midway segment meets the preset condition and the time length is longer than a preset threshold.

11. The device according to claim 9,

wherein the calculating calculates an accumulated sound volume of at least one of the sound signals in the breathing segments immediately before and immediately after the midway segment, and determines that the midway segment is an apnea episode when the acoustic feature of the sound signal in the midway segment meets the preset condition and the accumulated sound volume is larger than a preset threshold.

12. The device according to claim 9,

wherein the calculating calculates a difference in accumulated sound volume between the sound signals in the breathing segments immediately before and immediately after the midway segment, and determines that the midway segment is an apnea episode when the acoustic feature of the sound signal in the midway segment meets the preset condition and the difference in accumulated sound volume is less than a preset threshold.

13. The device according to claim 9,

wherein the calculating calculates a spectrum distance between the sound signals in the breathing segments immediately before and immediately after the midway segment, and determines that the midway segment is an apnea episode when the acoustic feature of the sound signal in the midway segment meets the preset condition and the spectrum distance is less than a preset threshold.

14. An apnea episode determination method comprising:

detecting a breathing segment and a midway segment from a sound signal during sleep, the breathing segment being considered to include a breathing sound, the midway segment existing in between the breathing segments;

calculating, by a computer processor, an acoustic feature based on a background noise component and a signal component excluding the background noise component, which are included in the midway segment; and

determining that the midway segment is an apnea episode when the acoustic feature meets a preset condition.

15. A computer-readable storage medium storing an apnea episode determination program that causing a computer to execute a process comprising:

detecting a breathing segment and a midway segment from a sound signal during sleep, the breathing segment being considered to include a breathing sound, the midway segment existing in between the breathing segments;

calculating an acoustic feature based on a background noise component and a signal component excluding the background noise component, which are included in the midway segment; and

determining the midway segment as an apnea episode when the acoustic feature meets a preset condition.