Vibroacoustic earbud

1. A vibroacoustic earbud (“earbud”), comprising:

a housing including a nozzle that is configured for positioning within an ear canal of an individual, and an infrasonic/vibration sensor included within the nozzle that detects biosignals including infrasonic signals from a body of the individual in the ear canal;

a nozzle tip configured to engage with a wall of the ear canal to create an earbud seal, forming an ear canal acoustic volume that amplifies the biosignals in the ear canal;

wherein due to an unintentional leak that occurs in the earbud seal that possibly reduces an acoustic pressure in the ear canal acoustic volume, the earbud is tuned to minimize loss of amplitude of the biosignals detected by the sensor in the ear canal acoustic volume; and

wherein the earbud is tuned to limit a low frequency biosignal roll off in a biosignal transfer function of the earbud, wherein the biosignal transfer function relates an acoustic pressure at the infrasonic/vibration sensor to the acoustic pressure in the ear canal acoustic volume, and wherein the acoustic pressure in the ear canal acoustic volume is produced by the biosignals.

2. The earbud of claim 1 , wherein the low frequency biosignal roll off is between −15 dB and 0 dB at 1 Hz.

3. The earbud of claim 1 , wherein a −3 dB frequency of the low frequency biosignal roll off is approximately 3 Hz.

4. The earbud of claim 1 , wherein the low frequency biosignal roll off drops no more than approximately 3 dB between 3 Hz and 1 Hz.

5. The earbud of claim 1 , further comprising a speaker within the housing, and wherein the earbud is tuned by selecting a speaker with a speaker effective acoustic volume that is less than or equal to ½ that of the ear canal acoustic volume.

6. The earbud of claim 1 , further comprising a speaker within the housing, wherein the earbud is tuned to limit an audio signal roll off in an audio transfer function of the earbud, and wherein the audio transfer function relates a voltage driving the speaker to the acoustic pressure in the ear canal acoustic volume, and wherein the acoustic pressure in the ear canal acoustic volume is produced by audio signals presented at the ear canal by the speaker.

7. The earbud of claim 6 , wherein the audio signal roll off is between −15 dB and 0 dB at 1 Hz.

8. The earbud of claim 1 , further comprising:

a rear housing portion and a front housing portion, and an internal tuned port located between the rear housing portion and the front housing portion;

wherein the earbud is tuned by constructing the internal tuned port and the nozzle to each provide intentional leaks within the earbud such that the intentional leak provided by the internal tuned port relative to the intentional leak provided by the nozzle is in a range of ratios between 1:1 and 4:1.

9. The earbud of claim 1 , wherein the earbud is tuned to provide an overall intentional leak within the earbud, the value of which is on the order of the unintentional leak.

10. A vibroacoustic earbud (“earbud”) method, the method comprising:

positioning a nozzle of a housing of the earbud within an ear canal of an individual, and an infrasonic/vibration sensor included within the nozzle detecting biosignals including infrasonic signals from a body of the individual in the ear canal;

engaging a nozzle tip of the nozzle with a wall of the ear canal to create an earbud seal, the result of which forms an ear canal acoustic volume that amplifies the biosignals in the ear canal, the earbud tuned to minimize loss of amplitude of the biosignals detected in the ear canal acoustic volume by the sensor, the loss of amplitude of the biosignals being the result of an unintentional leak occurring in the earbud seal that possibly reduces acoustic pressure in the ear canal acoustic volume;

wherein the earbud tuned to minimize loss of amplitude of the biosignals detected in the ear canal comprises limiting a low frequency biosignal roll off in a biosignal transfer function of the earbud, the biosignal transfer function relating an acoustic pressure at the infrasound/vibration sensor to the acoustic pressure in the ear canal acoustic volume, and the acoustic pressure in the ear canal acoustic volume being produced by the biosignals.

11. The method of claim 10 , further comprising the low frequency biosignal roll off being between −15 dB and 0 dB at 1 Hz.

12. The method of claim 10 , further comprising a −3 dB frequency of the low frequency biosignal roll off being approximately 3 Hz.

13. The method of claim 10 , further comprising the low frequency biosignal roll off dropping no more than approximately 3 dB between 3 Hz and 1 Hz.

14. The method of claim 10 , wherein the earbud tuned to minimize loss of amplitude of the biosignals detected in the ear canal comprises limiting an audio signal roll off in an audio transfer function of the earbud, the audio transfer function relating a voltage driving a speaker of the earbud to the acoustic pressure in the ear canal acoustic volume, and the acoustic pressure in the ear canal acoustic volume being produced by audio signals presented at the ear canal by the speaker.

15. The method of claim 14 , further comprising the audio frequency roll off being between −15 dB and 0 dB at 1 Hz.

16. The method of claim 14 , further comprising a −3 dB frequency of the audio frequency roll off being approximately 3 Hz.

17. The method of claim 14 , further comprising the audio frequency roll off dropping no more than approximately 3 dB between 3 Hz and 1 Hz.

18. The method of claim 10 , wherein the earbud tuned to minimize loss of amplitude of the biosignals detected in the ear canal comprises:

locating an internal tuned port between a rear housing portion and a front housing portion of the earbud; and

constructing the internal tuned port and the nozzle to each provide intentional leaks within the earbud such that the intentional leak provided by the internal tuned port relative to the intentional leak provided by the nozzle is in a range of ratios between 1:1 and 4:1.

19. The method of claim 10 , wherein the earbud tuned to minimize loss of amplitude of the biosignals detected in the ear canal comprises providing an overall intentional leak within the earbud, the value of which is on the order of the unintentional leak.