Hearing Screening Systems (Technical Manual)
14
2.3. Arrangement and Operation
The screening system is intended for the performing of two test types: OAE and ABR.
The principle of operation at OAE performing is based on the registration of the
auditory fluctuations of the cochlea OHC with the use of the probe microphone, in
response to the auditory stimulation with the use of the telephones built in the probe.
The principle of operation at ABR performing is based on the registration of the brain
electrical response in reply to the auditory stimulation.
The functional scheme of
Neuro-Audio-Screen
screening system is presented in
the Fig. 1.
PU amplifier
Microphone
amplifier
Telephone
amplifier
ADC
DAC
CPM
LCD
Keyboard
Bluetooth module
Secondary power
supply source
Rechargeable
batteries
Biopotentials
electrodes
Probe microphone
Probe telephones
Headphones
External power
9 V
Fig. 1
In the OAE test mode, the central processor module (CPM) generates the test signal
in a digital form and transfers it to the digital-to-analogue converter (DAC). The DAC
converts the signal to the analogue form and directs to the amplifier. After that, the
signal from the amplifier is transferred to the OAE probe telephones where it is
converted to the acoustic stimulus. The acoustic response of the cochlea OHC is
registered by the probe microphone and is converted to the electrical signal. Via the
microphone amplifier this signal is transferred to the analogue-to-digital converter
(ADC) input where it is converted to the digital form. The digitized response is directed
to CPM where it is processed and analyzed. The report concerning the test results is
based on the CPM analysis.
In the ABR test mode, the device operates in the same way. CPM generates the test
signal which is converted into the analogue form when transferring via the DAC, is
amplified by the amplifier and is directed either to the OAE probe telephones or to the
