Earphones for measuring and entraining respiration

1. A system comprising:

an earphone comprising:

a loudspeaker;

a microphone;

a housing supporting the loudspeaker and the microphone; and

an ear tip surrounding the housing, the ear tip being configured to acoustically couple both the loudspeaker and the microphone to an ear canal of a user, and to acoustically close the entrance to the user's ear canal;

a second earphone comprising:

a second loudspeaker;

a second microphone;

a second housing supporting the second loudspeaker and the second microphone; and

a second ear tip surrounding the second housing, the second ear tip being configured to acoustically couple both the second loudspeaker and the second microphone to a second ear canal of the user, and to acoustically close the entrance to the user's second ear canal; and

a processor configured to:

receive input audio signals from the microphone;

receive second input audio signals from the second microphone;

detect peaks having a frequency of around 1 Hz in the input audio signals by combining the input audio signals from the first microphone with the second input audio signals, and detecting peaks within the result of the combination;

based on the detected peaks, compute an instantaneous heart rate;

measure a frequency of an oscillation within the instantaneous heart rate; and

based on the frequency of the oscillation, compute a rate of respiration.

2. The system of claim 1 , wherein the processor is configured to measure the frequency of the oscillation within the instantaneous heart rate by computing a fast Fourier transform (FFT) of the instantaneous heart rate.

3. The system of claim 1 , wherein the processor is configured to measure the frequency of the oscillation within the instantaneous heart rate by

computing a gradient of the instantaneous heart rate; and

computing a fast Fourier transform (FFT) of the gradient of the instantaneous heart rate.

4. The system of claim 1 , wherein the processor is configured to measure the frequency of the oscillation within the instantaneous heart rate by detecting peaks of the instantaneous heart rate.

5. The system of claim 1 , wherein the processor is configured to measure the frequency of the oscillation within the instantaneous heart rate by fitting a sine function to the instantaneous heart rate, the frequency of the sine curve being the frequency of the oscillation.

6. The system of claim 1 , wherein combining the input audio signals comprises multiplying the amplitudes of the first and second input audio signals, at each time that the two signals are sampled.

7. The system of claim 1 , wherein the processor is further configured to adjust output audio signals based on the rate of respiration, and provide the output audio signals to the loudspeaker.

8. The system of claim 7 , wherein adjusting the output audio signals comprises adjusting a rhythm of the output audio signals to be about one cycle per minute less than the detected respiration rate.

9. The system of claim 7 , wherein adjusting the output audio signals comprises transitioning the output audio signals from respiration entrainment sounds to masking sounds.

10. The system of claim 7 , wherein adjusting the output audio signals comprises transitioning the output audio signals from masking sounds to awakening sounds.

11. The system of claim 7 , wherein

the earphone further includes a memory storing sound files; and

providing the output audio signals comprises retrieving a first sound file from the memory.

12. The system of claim 11 , wherein adjusting the output audio signals comprises retrieving a second sound file from the memory and using the second sound file to generate the output audio signals.

13. The system of claim 1 , wherein the processor is integrated within the earphone.

14. The system of claim 1 , wherein the processor is integrated within a portable computing device.

15. A method of measuring a respiration rate of a user of an earphone, the method comprising:

receiving input audio signals from a microphone supported by a housing and acoustically coupled to the user's ear canal by an ear tip surrounding the housing, the ear tip acoustically closing the entrance to the user's ear canal;

receiving second input audio signals from a second microphone supported by a second housing and acoustically coupled to the user's second ear canal by a second ear tip surrounding the second housing, the second ear tip acoustically closing the entrance to the user's second ear canal; and

in a processor,

detecting peaks having a frequency of around 1 Hz in the input audio signals by combining the input audio signals from the first microphone with the second input audio signals, and detecting peaks within the result of the combination,

based on the detected peaks, computing an instantaneous heart rate,

measuring a frequency of an oscillation within the instantaneous heart rate, and

based on the frequency of the oscillation, computing a rate of respiration.

16. The method of claim 15 , wherein measuring the frequency of the oscillation within the instantaneous heart rate comprises computing a fast Fourier transform (FFT) of the instantaneous heart rate.

17. The method of claim 15 , wherein measuring the frequency of the oscillation within the instantaneous heart rate comprises:

computing a gradient of the instantaneous heart rate; and

computing a fast Fourier transform (FFT) of the gradient of the instantaneous heart rate.

18. The method of claim 15 , wherein measuring the frequency of the oscillation within the instantaneous heart rate comprises detecting peaks of the instantaneous heart rate.

19. The method of claim 15 , wherein measuring the frequency of the oscillation within the instantaneous heart rate comprises fitting a sine function to the instantaneous heart rate, the frequency of the sine curve being the frequency of the oscillation.

20. The method of claim 15 , wherein combining the input audio signals comprises multiplying the amplitudes of the first and second input audio signals, at each time that the two signals are sampled.

21. The method of claim 15 , further comprising, in the processor:

adjusting output audio signals based on the rate of respiration, and

providing the output audio signals to the loudspeaker.