System for estimating sound pressure levels at the tympanic membrane using pressure-minima based distance

1. A method, comprising:

providing an apparatus configured to measure sound in an ear canal of a wearer's ear at a distance from a tympanic membrane of the ear;

measuring sound at a single location in the ear received by the apparatus to produce a signal;

performing frequency analysis on the signal to determine output as a function of the frequency;

determining a null frequency of a minima of the output according to the measurement at the single location;

calculating a distance equal to a quarter wavelength of the null frequency;

retrieving a previously generated correction factor associated with the quarter wavelength;

applying the correction factor to the output to generate a corrected output; and

producing an estimated sound pressure level at the tympanic membrane from the corrected output.

2. The method of claim 1 , wherein performing the frequency analysis includes performing a fast Fourier transform (FFT) on the signal.

3. The method of claim 1 , wherein the correction factor is a function of width of the minima.

4. The method of claim 1 , wherein the correction factor is a function of depth of the minima.

5. The method of claim 1 , further comprising generating a complex tone for sound measurement by the apparatus.

6. The method of claim 5 , wherein generating a complex tone for sound measurement includes:

generating a complex test tone with frequencies separated by 50 Hz.

7. The method of claim 5 , wherein generating a complex test tone for sound measurement includes:

generating a complex test tone with frequencies at or above 100 Hz and at or below 16000 Hz.

8. The method of claim 1 , further comprising generating a swept tone for sound measurement by the apparatus.

9. The method of claim 1 , further comprising:

outputting the estimated sound pressure level at the tympanic membrane from the corrected output on a display device.

10. An apparatus for measuring sound pressure level of sound in an ear canal at a tympanic membrane, comprising:

an audio output device to play the sound;

a microphone configured to receive the sound in the ear canal at a first distance from the tympanic membrane and to provide a signal based on the received sound; and

a processor executing instructions configured to:

perform frequency analysis on the signal and determine output as a function of frequency;

determine a null frequency of a minima of the output according to a single measurement at the first distance;

calculate a second distance equal to a quarter wavelength of a wave at the null frequency;

retrieve a previously generated correction factor associated with the second distance, and

apply the correction factor to the output to generate a corrected output related to an estimated sound pressure level at the tympanic membrane.

11. The apparatus of claim 10 , wherein the processor is programmed to perform an FFT on the signal.

12. The apparatus of claim 10 , wherein the correction factor is a function of width of the minima.

13. The apparatus of claim 10 , wherein the correction factor is a function of depth of the minima.

14. The apparatus of claim 10 , wherein the sound is a complex tone.

15. The apparatus of claim 14 , wherein the complex is a complex tone with frequencies at or above 100 Hz and at or below 16000 Hz.

16. The apparatus of claim 14 , wherein the complex is a complex tone with frequencies separated by 50 Hz.

17. The apparatus of claim 10 , wherein the sound is a swept tone.

18. The apparatus of claim 10 , further comprising a display device to present the estimated sound pressure level at the tympanic membrane from the corrected output.

19. The apparatus of claim 10 , further comprising a probe, wherein the probe is attached to the audio output device.

20. The apparatus of claim 10 , wherein the processor is configured to send the sound wirelessly to the audio output device.