Receiver and Sound Bore

Question 1

What do receivers do?

Answer 1

They transduce the amplified electrical signal back to an acoustic signal

Question 2

Over the years, was the size of the device determined by the receiver?

Answer 2

Yes

Question 3

How does a receiver work?

Answer 3

Coil of wire, magnet, and a diaphragm
Armature is balanced between two magnets like a diving board
As an electrical current flows through the coil, the armature is magnetized and pulled toward one magnet or the other
The armature is connected to a diaphragm, its movement pushes and pulls the air creating an acoustic signal

Question 4

Does the physical size of the receiver determine the output capabilities of the device?

Answer 4

Yes, larger receivers produce a higher output

Question 5

What receivers have a better high freq response?

Answer 5

Smaller ones
The diaphragm is smaller and stiffer

Question 6

What is the solution when high freq and low freq gain is needed?

Answer 6

Two receiver system
The output from both receivers is summed before reaching the TM
One optimizes low freq and the other optimizes high freq

Question 7

What are some of the benefits to two receiver devices?

Answer 7

Both HF and LF output
Reduced battery drain
Minimizes potential of saturation distortion

Question 8

What is receiver saturation?

Answer 8

When an output signal exceeds the capabilities of the receiver
Peak-clipping and battery drain occurs

Question 9

What are other limitations of receivers?

Answer 9

Shock damage (vibration of dislodged receiver adds distortion)
Increased consumption reduces battery life
Receivers are susceptible to damage from moisture or cerumen

Question 10

What are some physical properties that change the final output of the device?

Answer 10

Venting
Sound bore
Damping

Question 11

Do RICs have a sound bore?

Answer 11

No

Question 12

What is the sound bore path?

Answer 12

The column of air a soundwave passes through as it leaves the receiver and arrives to the TM

Question 13

Can standing waves occur at the sound bore?

Answer 13

Yes
Reflection in the sound bore can cause the wave to overlap with itself

Question 14

How do thin tubes change the frequency response and peak frequency?

Answer 14

A reduction in the hearing aid HF output by 5-10 dB is seen above 1000 Hz
The tubing resonance shifts down to about 800 Hz from 1000 Hz

Question 15

How do libby horns impact the high frequency output of the device?

Answer 15

It increases the high freq output
Need to have a certain length of the horn to experience the benefit

Question 16

Do smaller volumes between the end of the mold and the TM increase the output SPL at the TM?

Answer 16

Yes
Decreased length = increased SPL for all freq
Slightly higher gain for high freq

Question 17

What do dampers do?

Answer 17

They smooth the peaks and throughs of the freq response
Loses energy as it passes through the damping material

Question 18

What is the amount of acoustic resistance applied by the damper referred to as?

Answer 18

Ohm
Higher ohms = higher resistance

Question 19

Are acoustic dampers color coded?

Answer 19

Yes, the amount of damping they provide are assigned a color

Question 20

Does the dampers ability to break up air particles depend on the placement of the damper?

Answer 20

Yes

Question 21

What is the most practical location for a damper?

Answer 21

At the tip of the BTE earhook

Question 22

Are clogged dampers a common cause of device malfunction?

Answer 22

Yes
It is like water on a screen door