Receiver and Sound Bore Flashcards
What do receivers do?
They transduce the amplified electrical signal back to an acoustic signal
Over the years, was the size of the device determined by the receiver?
Yes
How does a receiver work?
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
Does the physical size of the receiver determine the output capabilities of the device?
Yes, larger receivers produce a higher output
What receivers have a better high freq response?
Smaller ones
The diaphragm is smaller and stiffer
What is the solution when high freq and low freq gain is needed?
Two receiver system
The output from both receivers is summed before reaching the TM
One optimizes low freq and the other optimizes high freq
What are some of the benefits to two receiver devices?
Both HF and LF output
Reduced battery drain
Minimizes potential of saturation distortion
What is receiver saturation?
When an output signal exceeds the capabilities of the receiver
Peak-clipping and battery drain occurs
What are other limitations of receivers?
Shock damage (vibration of dislodged receiver adds distortion)
Increased consumption reduces battery life
Receivers are susceptible to damage from moisture or cerumen
What are some physical properties that change the final output of the device?
Venting
Sound bore
Damping
Do RICs have a sound bore?
No
What is the sound bore path?
The column of air a soundwave passes through as it leaves the receiver and arrives to the TM
Can standing waves occur at the sound bore?
Yes
Reflection in the sound bore can cause the wave to overlap with itself
How do thin tubes change the frequency response and peak frequency?
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
How do libby horns impact the high frequency output of the device?
It increases the high freq output
Need to have a certain length of the horn to experience the benefit
Do smaller volumes between the end of the mold and the TM increase the output SPL at the TM?
Yes
Decreased length = increased SPL for all freq
Slightly higher gain for high freq
What do dampers do?
They smooth the peaks and throughs of the freq response
Loses energy as it passes through the damping material
What is the amount of acoustic resistance applied by the damper referred to as?
Ohm
Higher ohms = higher resistance
Are acoustic dampers color coded?
Yes, the amount of damping they provide are assigned a color
Does the dampers ability to break up air particles depend on the placement of the damper?
Yes
What is the most practical location for a damper?
At the tip of the BTE earhook
Are clogged dampers a common cause of device malfunction?
Yes
It is like water on a screen door
