Electroacoustical Coupler Measurements

Question 1

How are coupler measurements performed

Answer 1

Coupler measurements are performed inside a sound chamber using a devise called a coupler. The coupler acts as a substitute for the ear canal , providing a standard sized cavity into which the amplification produced by the HA is directed and a mechanical way to attach a microphone to the HA.

Question 2

What is the primary use of a coupler measurement?

Answer 2

To specify the characteristics of a HA and to determine if it is functioning properly. They are faster to do than REM’s but are not precise measurements of the frequency response of the HA inside the ear.

Question 3

How can Coupler Measurements be used

Answer 3

To check:

• That the HA is performing to manufacturer specifications
• To Pre-Fit a HA before client arrives at clinic
• Establish a baseline that can be used later if the HA comes back for repair/adjustment

Question 4

What is a Coupler Measurement?

Answer 4

Is the electroacoustical analysis of a HA connected to a coupler inside a sound occluded box known as a sound chamber. Tests are performed in the controlled environment of the sound chamber and do not require wearer.

Question 5

Frequency response achieved with a standard 2cc coupler can be quite different than the response of the HA inside the ear. What are some disadvantages that the coupler measurements do not take into account?

Answer 5

Venting
The shape of the HA
Any irregularities that may exist inside the Pt’s ear canal

Question 6

2-cc Coupler’s are designed for what type of HA’s.

Answer 6

BTE’s and ITE’s

Question 7

2-cc Couplers are especially unrealistic for the measurement of what type of HA’s and why

Answer 7

CIC’s because of the deeper insertion depths of the canal HA’s create a greater overall amplification than more traditional Styles

Question 8

Which Coupler is used to test BTE’s when performing sound chamber measurements

Answer 8

HA-2

Question 9

Which coupler is used to test ITE, ITC and CIC HA’s when performing sound chamber measurements

Answer 9

HA-1 Couplers

Question 10

Which couplers are used to test OTE - Open Over the ear HA when performing Sound chamber measurements

Answer 10

Sometimes they are tested with HA-1 coupler combined with a special coupler device….other times with a HA-2 Coupler

Question 11

ANSI 96: Full on gain Frequency sweep taken at 90 dB

Answer 11

OSPL 90

Question 12

The difference between the output SPL and the input SPL in the 2 cc coupler

Answer 12

Acoustic Gain

Input+ GAIN=Output

Question 13

A user operated control for adjusting gain, the volume wheel

Answer 13

Gain Control

Question 14

Any control that effects the steady state operation of the AGC function excluding the user operated gain control, any tone control or a peak clipping control

Answer 14

AGC control

Question 15

Where the curve first departs from linear by 2 dB at input levels below the compression or limiting portion of the curve

Answer 15

AGC Kneepoint

Question 16

A HA with microphone sensitivity dependent on the direction of sound

Answer 16

Directional microphones

Question 17

SSPL 90

Answer 17

Saturation sound pressure level for 90 dB input

Question 18

HFA SSPL 90

Answer 18

High frequency average saturation sound pressure level for 90 dB

Is the average of the SSPL 90 values at 1k, 1600Hz and 2500Hz

Question 19

FOG

Answer 19

Full on Gain- the acoustic gain the HA produces with a sinusoid always 60dB input when the VC is full on

Question 20

HFA-FOG

Answer 20

High Frequency Average Full on gain- the average of the full on gain values at 1000Hz, 1600Hz and 2500Hz

Question 21

Harmonic Distortion

Answer 21

Occurs when new frequencies generated are harmonics of the original input signal.

Question 22

HFA SSPL 90-17dB is what

Answer 22

Reference Test position

Question 23

How do you find the reference test gain

Answer 23

HF SSPL 90- 17-60 or 90-77

Is the difference between output and input levels

Question 24

_____Is a measure of how much a hearing aid distorts a signal that it is amplifying.

Answer 24

Total Harmonic Distortion- Whenever a pure tone signal is amplified harmonics of this signal are created.THD is the percentage of these harmonics as compared to the total signal produced by the HA.

Question 25

____is the measurement of the internal noise of the HA

Answer 25

EIN- Equivalent Input Noise- It is the difference between a measurement taken with a 60dB (96)SPL signal or a 50 dB SPL (03)signal, and a measurement taken without an input signal

Question 26

What is the TMFS

Answer 26

Telephone Magnetic Field Simulator - it is designed to test the telecoil within the HA and is designed to simulate the magnetic field created by a telephone receiver.

Question 27

What does the Input/output measurement do

Answer 27

Characterizes the compression present in the HA. It is tested on AGC HA’s only.