his 140 - hi systems and adjustable parameters

HI Systems & Adjustable

Parameters

Custom hearing instruments systems

include:

1. In-the-ear (ITE)

2. In-the-canal (ITC)

3. Completely-in-the-canal (CIC)


Parameters

These three custom systems are

comprised of two basic pieces.

They are:

1. The faceplate

2. The custom shell


Parameters

Another system is a modular hearing

instrument system. It utilizes a faceplate

and shell design however, the shell is not

custom. This modular construction can be

manufactured in a more automated

manner resulting in reduced production

costs.


Parameters

The behind-the-ear (BTE) hearing system

is designed with all of the components

housed inside a casing. This casing is

generally of a shape which lends itself to a

comfortable fit behind the Pinna.


Parameters

All of these basic systems have the following basic components for achieving hearing instrument amplification performance.

1. Microphone (input transducer)

2. Amplifier

3. Volume control

4. Receiver (output transducer)


Parameters

Adjustable parameters which may be

available in all systems are:

1. Frequency response filtering

2. Gain and Power

3. Compression


Parameters

Frequency and response filtering

include: Low-cut slope

High-cut slope

Cross-over frequency

Low frequency gain

High frequency gain

Balance of low and high frequencies


Parameters

Gain and power include:

SSPL (output) peak clipping

Gain—overall amplification gain


Parameters

Compression:

Compression ratio

Compression threshold

Gain for low level inputs

Gain for high level inputs


Parameters

All of these adjustable parameters may be

written into digital algorithms. These

algorithms are used in the performance

characteristics of digital hearing

instruments.


Parameters

At the beginning of the year 2000, the

majority of hearing instruments dispensed

in the United States were analog—not

digital.


Parameters

Within this past decade, the

evolution/transition now reflects that the

majority of hearing instruments dispensed

in the United States are digital.

Many of the adjustable parameters used in

the fitting of analog hearing instruments

are now written into digital algorithms.


Parameters

There are two basic processing

parameters used in digital hearing

instruments. They are:

1. Sequential processing

2. Block or frame processing


Parameters

These two basic strategies differ

between the method with which each

processes frequency input

information into the amplifier.


Parameters

When the frequencies of the incoming

signal from the microphone is

processed at the same rate as it

received by the analog to digital

converter, it is considered to be

sequential processing.


Parameters

When the frequencies are framed or

blocked before reaching the amplifier it is

termed block processing. Calculations are

created upon the input frequencies before

any digital computations occur.


Parameters

These calculations of frequencies occur by

a process termed Fast Fourier Transform.

We will learn much more regarding FFT in

our study of compression and digital

algorithms.


Parameters

Digital hearing instrument systems have some fundamental electronic performance differences from analog technology.

Digital hearing instruments are rated in their performance by three fundamental processing items.


Parameters

The three fundamental processing

characteristics of digital hearing

instruments are:

1. Sampling rate

2. Instructions per second

3. Number of bits

his 140 - hi systems and adjustable parameters

Technology

basic systems

custom systems

digital algorithms

analog hearing instrumentsare

high frequencies

ear bte hearing systemis

basic processingparameters

basic pieces