Respiratory monitors and monitoring methods

1. A respiratory monitor comprising:

a sensor configured to generate a sensor signal indicative of both respiration-related motion and respiration-related sound, the sensor including:

a single accelerometer configured for attachment to a respiring subject and measuring an acceleration A=G·cos(φ) where A is the acceleration measured by the accelerometer, G is the magnitude of the gravitation vector, and φ is an orientation angle of the accelerometer,

a magnetometer coupled with the accelerometer such that the accelerometer and the magnetometer have a common orientation; and

a signal processor configured to generate the sensor signal based on the acceleration measured by the accelerometer and a magnetometer signal output by the magnetometer;

a first filter configured to generate a respiration-related motion monitoring signal indicative of respiration-related motion by extracting from the sensor signal a low frequency signal encompassing frequencies of respiration-related motion;

a second filter configured to generate a sound monitoring signal indicative of respiration-related sound by extracting from the sensor signal a high frequency signal encompassing frequencies of respiration-related sound, the respiration-related sound monitoring signal being based on the high frequency signal; and

a signals synthesizer configured to synthesize a respiratory monitor signal by combining the respiration-related motion monitoring signal and the respiration-related sound monitoring signal to form the respiratory monitor signal.

2. The respiratory monitor as set forth in claim 1 , wherein the second filter further comprises:

an envelope filter or extractor configured to generate an envelope signal corresponding to an envelope of the high frequency signal, the respiration-related sound monitoring signal being based on the envelope signal.

3. The respiratory monitor as set forth in claim 1 , wherein the accelerometer and the magnetometer are monolithically integrated on a common substrate.

4. The respiratory monitor as set forth in claim 1 wherein:

the signals synthesizer is configured to synthesize the respiratory monitor signal by computing a cross-correlation of the respiration-related motion monitoring signal and the respiration-related sound monitoring signal.

5. A sensor for use in respiratory monitoring, the sensor comprising:

an accelerometer;

a magnetometer defining together with the accelerometer a unitary sensor configured for attachment to a respiring subject so as to move as a unit responsive to respiration-related motion of the respiring subject; and

a signal processor configured to generate a respiratory monitor signal based on a single signal comprising change as a function of time of the angle of a three degrees of freedom (3 DOF) rotation of the unitary sensor computed from an accelerometer signal output by the accelerometer and a magnetometer signal output by the magnetometer.

6. The sensor of claim 5 , wherein the signal processor is configured compute the 3 DOF rotation based on Euler angles.

7. The sensor of claim 5 , wherein the signal processor is configured compute the 3 DOF rotation based on a 3×3 rotation matrix.

8. The sensor of claim 5 , wherein the signal processor is configured compute the 3 DOF rotation using the axis-angle approach.

9. The sensor of claim 5 , wherein the signal processor is configured compute the 3 DOF rotation using the quaternion approach.

10. A sensor for use in respiratory monitoring, the sensor comprising:

a single accelerometer measuring an acceleration A=G·cos(φ) where A is the acceleration measured by the accelerometer, G is the magnitude of the gravitation vector, and φ is an orientation angle of the accelerometer;

a single magnetometer defining together with the single accelerometer a unitary sensor configured for attachment to a respiring subject so as to move as a unit responsive to respiration-related motion of the respiring subject; and

a signal processor configured to generate a respiratory monitor signal based on change as a function of time of the angle of a three degrees of freedom (3 DOF) rotation of the unitary sensor computed from the acceleration measured by the single accelerometer and a magnetometer signal output by the single magnetometer.

11. The sensor of claim 10 , wherein the single accelerometer and the single magnetometer are monolithically integrated on a common substrate.