07_Intro to Real Ear Measurements

Question 1

What are the four steps in the workflow for individualization of hearing aids?

Answer 1

• assessment
• selection and prescription
• verification and fine tuning (probe mic)
• outcome assessment

Question 2

What are probe tbe microphone measurements?

Answer 2

Originally, (70’s) microphone was placed in the ear canal, but not the tube is calibrated and placed as close to the TM as possible, so it is as though the mic is in the canal

Question 3

Sound usually travels through the hearing instrument, then tubing, then earmold, then ear canal, to the ear drum. Name two possible feedback loops

Answer 3

Through the:

• vent
• leak
• transmission through earmold
• tissue and bone conduction

Question 4

Name 2 things ANSI standards do?

Answer 4

• help all manufacturers set up the same measurements the same way
• ensure understanding of what the measurements mean and how to make them

Question 5

If a term ends in G (for gain) does it refer to an absolute measure or a difference measurement?

Answer 5

Difference measurement; R (for response) refers to an absolute measure in SPL across frequencies.

Question 6

What word means that “the input level used to generate the response has been subtracted from the absolute output level across frequencies”?

Answer 6

“Gain”

Question 7

What does REUR stand for?

Answer 7

Real-ear unaided response

- the SPL, across frequencies, measured in the open (unaided) ear canal for a particular input signal

Question 8

What is real-ear unaided gain (REUG)?

Answer 8

The gain provided by the external ear, ear canal, and head diffraction effects of an individual measured in the ear canal.
- subtract the input signal level from the REUR across frequencies to obtain the REUG

Question 9

How is a REUR/REUG measured (step by step)?

Answer 9

• oto ax
• tube placed w/in 5 mm of TM
• patient seated appropriate distance from loudspeaker and at appropriate azimuth for testing (usually 0 degrees)
• select test signal and level
• conduct measurement

Question 10

Since we don’t use binocular otoscopes, our depth perception is off. Describe the landmark used to locate the tube placement near the TM

Answer 10

The third of the 3 bends in the EAM

- appears as a little “hill” near the TM

Question 11

In terms of patient comfort, what is the best way to insert the probe tube?

Answer 11

• start at intratragic notch
• slide tube along floor of EAM
  avoid flicking TM or sensitive parts

Question 12

How many pieces of cartilage make up the pinna?

Answer 12

One

Question 13

How many types of skeletal muscles make up the pinna?

Answer 13

2:
intrinsic (6)
extrinsic (3)

Absence of skeletal muscles may be the underlying cause of anomalies, such as microtia and external auditory canal atresia (aural atresia)

Question 14

What are the 3 main nerves of the pinna?

Answer 14

Auricle branch of the vagus nerve
Great auricular nerve
Auriculotemporal nerve

Question 15

What are the 2 main functions of the pinna?

Answer 15

• pick up sound waves

- facilitate vertical and front/back sound localization

Question 16

What 2 things does the head related transfer function (HRTF) depend on?

Answer 16

• shape of the auricle

- size of the auricle

Question 17

Describe the 2 parts of the EAM

Answer 17

Outermost:

• cartilaginous 1/3
• hair follicles, sweat, oil and cerumen glands

Innermost:

• bony 2/3
• thin skin
• canal is less mobile

*Deeper fit avoids cerumen, allows higher output, but very low tolerance for poor fit

Question 18

Which nerve innervates the laryngeal and pharyngeal muscles, and can cause queasiness if stimulated in the EAM of some individuals?

Answer 18

Vagus nerve

Question 19

Which nerve is involved in facial muscles, the salivary gland, and the stapedius muscle?

Answer 19

Facial nerve (VII)

Question 20

_____ (higher/lower) frequencies have a higher amount of error, the closer the tube is placed to the TM

Answer 20

Higher; the closer you move, the higher in frequency the standing wave is (e.g. 7 and 8 kHz have -12 dB at 1 cm, compared to -2 dB for 3 and 4 kHz.

Question 21

How far from the eardrum should the tube be placed in most adults? What are the exceptions?

Answer 21

5 mm

- exceptions: adults with deeply inserted fittings, and babies

Question 22

What are the typical insertion depths, from the intertragal notch, for:
Adult males
Adult females
Infants/children

Answer 22

Males: 30 mm
Females: 28 mm
Children: 25 mm

Question 23

How does the geometric method of probe tube placement differ from the constant depth method?

Answer 23

The ridge of the earmold corresponding to the location of the intertragal notch is identified, and the tube is laid along the bottom of the earmold

• the open end of the tube is placed so that it extends 5 mm beyond the tip of the hearing instrument
• can be taped in place on the earmold or aid
• *usually only used for young infants

Question 24

The geometric and constant depth probe tube placement methods can be combined into one method. Describe it

Answer 24

• mark insertion depth for correct age

- check that this is at least 5 mm beyond the sound bore (unless <6 month old infant)

Question 25

Name 3 tips for easier probe tube insertion

Answer 25

• tighten loops
• place probe tube in front of loop to prevent slippage
• fasten clip across patient’s shirt to hold probe module in place

Question 26

What does REAR stand for?

Answer 26

Real-ear aided response

• the frequency response of a hearing instrument that is turned on, measured in the ear canal, for a particular input signal
• “response” = measuring SPL