Amplification - Electroacoustic Characteristics Flashcards
The outer parts of HAs vary dramatically, but on the inside they are ___ _____
The same
What are the 5 steps in how an HA works?
1) the mic picks up the acoustic signal
2) converses it to an electrical signal
3) electrical signal is digitized then amplified
4) that signal is changed back to an electrical signal
5) then that to an acoustic signal and sent to the listeners ear
What do the electroacoustic characteristics of the HA describe?
The performance characteristics - how the HA modifies the sound as its processed by the HA
What are 2 electroacoustic/performance characteristics of the HA?
1) gain and frequency response
2) maximum output
How are electroacoustic characteristics of an HA measured?
And electroacoustic analysis (EAA)
What group specifies the procedures to be used in an EAA? Why is that needed?
The American National Standards Institute (ANSI)
Equal data/measurements from different HA companies
Where/why can EAAs be checked?
At HA clinics, to make sure HAs are working like they should
____________ sheets provided date on the _______ and _____________ charactersitcs of particular HA models
Specification
Features
Electroacoustic
How are specification sheets used by audiologists? (2)
1) select appropriate HAs for clients
2) determine if HA is in proper working order
What is gain?
How much amp the HA provides; difference between input and output
How can gain be described?
With a graphic representation of gain across frequency - known as the frequency response of the HA
The gain needed depends primarily on a persons _______ of HL
Degree
Greater degree of HL = more ____ needed to make speech audible
Gain
What is the general rule of thumb for the amount of gain required?
The gain should be about half to the degree of HL
A person with 60 dB HL will need about ____ dB of gain?
30
What is the maximum output of an HA?
The highest sound pressure generated by an HA regardless of input level
All HAs have a point where increases in the _____ level do not result in additional increases in ______
Input
Output
Why is a HA having a maximum output limit important?
If it didn’t have it loud noises would be too uncomfortable and at dangerous levels
What are the two possible methods used to limit maximum output?
1) peak clipping
2) compression (automatic gain control)
How does peak clipping work?
Cuts sound off it its too loud
What is the negative of peak clipping?
It’s not high quality sound, causes distortion
How does compression/AGC work?
Scales down the sound wave
Which method of limiting maximum output is better/modern?
Compression
Why do some clients prefer peak clipping?
Severe to profound HL clients may use the distraction as helpful acoustic cues
