# US 8,542,841 B2 · Method to estimate the sound pressure level at eardrum using measurements away from the eardrum

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- Number: US 8,542,841 B2
- Document ID: US8542841B2
- Status: Granted
- Kind: B2
- Application number: 12/685,295
- Filed: 2010-01-11
- Published: 2010-08-12
- Granted: 2013-09-24
- Earliest claimed: 2009-01-12
- Assignees: Starkey Laboratories, Inc.
- Applicants: Janice LoPresti; Tao Zhang
- Inventors: Janice LoPresti; Tao Zhang
- Web page: https://patentgrep.com/patent/US8542841B2

## CPC

- A61B 5/036: {by means introduced into body tracts (A61B5/032 and A61B5/035 take precedence)}
- A61B 5/12: Audiometering
- A61B 5/125: {objective methods}
- A61B 5/6817: {Ear canal}
- H04R 25/00: Electric hearing aids
- H04R 25/70: {Adaptation of deaf aid to hearing loss, e.g. initial electronic fitting}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

A method for measuring sound pressure at a tympanic membrane of a wearer's ear including a high frequency range with a hearing assistance device. The hearing assistance device comprises a processor connected to a sensor in the ear canal. The device provides a measure of the sound pressure level at the tympanic membrane of the wearer using a null frequency and a null Q measured at a distant position away from the tympanic membrane. The method does not require a precise knowledge of the ear canal, nor does it require an elaborate calibration step. In various embodiments, the present approach works at low and high frequencies.

## Claims

### Claim 1

A method for measuring an estimated sound pressure level at a tympanic membrane in an ear canal of an ear of a wearer of a hearing assistance device using measurements away from the tympanic membrane, the method comprising:
placing a sound sampling apparatus in the ear canal at a first position;
placing a sound emitter in the ear canal at a second position;
generating sound with the sound emitter and receiving sound with the sound sampling apparatus to measure an amplitude response of the ear canal; and
determining the estimated sound pressure level at the tympanic membrane using measurements of sound from the sound sampling apparatus including measurements of a null frequency and a null Q at the first position and the measured amplitude response.

### Claim 2 (depends on 1)

The method of claim 1, wherein determining the estimated sound pressure level at the tympanic membrane includes:
determining a modeled sound pressure level at the tympanic membrane and a modeled sound pressure level at the first position using the null frequency and the null Q; and
determining the estimated sound pressure level at the tympanic membrane using measurements of sound from the sound sampling apparatus at the first position, the modeled sound pressure levels at the tympanic membrane, and the modeled sound pressure levels at the first position.

### Claim 3 (depends on 2)

The method of claim 2, further comprising determining the null Q by dividing the null frequency by a measured width of the amplitude response at the null frequency.

### Claim 4 (depends on 3)

The method of claim 3, further comprising:
modeling the ear canal as a cascade of cylindrical tubes, each tube of the cascade of tubes having a radius and a length, the cascade of tubes including two middle lengths L1 and L2 which are calculated from:
L1+L2=(5.81×105−Square Root[3.38×1011−7.92×107×(8450−f0)])/(3.96×107), where f0 is the null frequency; and
estimating a series resistance, R, in a middle ear analog using:
R=(5.92×10−3−Square Root[3.50×10−5+1.29×10−6×(2.78−Q)])/(6.46×10−7), where Q is the null Q.

### Claim 5 (depends on 2)

The method of claim 2, wherein placing a sound sampling apparatus comprises placing a thin tube with an end at the first position for sampling sound at the first position.

### Claim 6 (depends on 5)

The method of claim 5, further comprising placing a second end of the thin tube in a microphone port of the hearing assistance device.

### Claim 7 (depends on 2)

The method of claim 2, wherein placing a sound sampling apparatus comprises placing a microphone at the first position.

### Claim 8 (depends on 2)

The method of claim 2, wherein the sound sampling apparatus is a microphone fitted with a small sound tube and wherein the sound emitter is a receiver.

### Claim 9 (depends on 2)

The method of claim 2, wherein the first position and the second position have a minimum distance of about 5 mm.

### Claim 10 (depends on 2)

The method of claim 2, further comprising playing a swept audio sound into the ear canal by the hearing assistance device.

### Claim 11 (depends on 2)

The method of claim 2, further comprising playing a tone complex into the ear canal by the hearing assistance device.

### Claim 12 (depends on 2)

The method of claim 2, further comprising:
Estimating the decibels (dB) of sound pressure level (SPL) at the tympanic membrane (TM) from:
Estimated dB SPL at TM=Actual dB SPL at the first position+(Modeled dB SPL at TM−Modeled dB SPL at the first position).

### Claim 13 (depends on 1)

The method of claim 1, wherein placing a sound sampling apparatus comprises placing a thin tube with an end at the first position for sampling sound at the first position.

### Claim 14 (depends on 13)

The method of claim 13, further comprising placing a second end of the thin tube in a microphone port of the hearing assistance device.

### Claim 15 (depends on 1)

The method of claim 1, wherein placing a sound sampling apparatus comprises placing a microphone at the first position.

### Claim 16 (depends on 1)

The method of claim 1, wherein the sound sampling apparatus is a microphone fitted with a small sound tube and wherein the sound emitter is a receiver.

### Claim 17 (depends on 1)

The method of claim 1, wherein the first position and the second position have a minimum distance of about 5 mm.

### Claim 18 (depends on 1)

The method of claim 1, further comprising playing a swept audio sound into the ear canal by the hearing assistance device.

### Claim 19 (depends on 1)

The method of claim 1, further comprising playing a tone complex into the ear canal by the hearing assistance device.

### Claim 20 (depends on 1)

The method of claim 1, further comprising:
Estimating the decibels (dB) of sound pressure level (SPL) at the tympanic membrane (TM) from:
Estimated dB SPL at TM=Actual dB SPL at the first position+(Modeled dB SPL at TM−Modeled dB SPL at the first position).

### Claim 21 (depends on 1)

The method of claim 1, wherein the method is performed by the hearing assistance device and a fitting system.

### Claim 22 (depends on 1)

The method of claim 1, wherein the method is performed by the hearing assistance device.