Practical Questions Flashcards
Amplification practical
American National Standards Institute
- specifies electrical equipment standards
- specifies human related standards, and defines test protocols and normative data
Spec Sheet
compare in office performance to a set of measurement standards
acoustic chamber designed
to reduce reflections
Low ambient room noise
ambient noise cant affect results more than 0.5 dB
Test signal 10 dB louder than ambient noise
calibrated sound source consists of
testbox speakers and reference microphone
measurement microphone collects
signals exiting the device
reference microphone calibrates the
SPL output from speakers
- monitors signal intensity and automatically adjust speaker volume to maintain proper intensity
coupler microphone is a
measurement microphone sealed into the coupler that collects the output data from the hearing aid
Which coupler do we use
HA-2 Coupler
ANSI Standard pre measurement set up, devices must be adjusted what kind of settings?
Test mode settings
Testmode settings: settings in device must be set to provide the highest possible output
- internal gain settings maximized
- volume control maximized
- compression minimized to 1:1 (linear)
- set to broadcast frequency response
ANSI standard requires what measurements?
OSPL 90
Full on gain @ 50 dB
Reference test gain @ 60 dB
Total Harmonic Distortion
Equivalent Input noise
OSPL 90 - output SPL @ 90 dB
identifies the loudest possible output point the device can produce for a 90 dB input signal
- represents single frequency
GREEN PEAK LINE
HFA OSPL 90 - high frequency average output SPL @ 90dB
Calculates the average OSPL @ 90 output for 1K, 1.6K, 2.5k HZ
3 green triangles at bottom of screen
(maximum output of HA wont exceed UCL)
HFA/FOG
High Frequency Average full on gain
shows average gain for 1,1.6, and 2.5 kHZ for a 50 dB SPL Input signal
Reference Test Gain (reduce volume after HFA FOG)
output 17dB below HFA FOG @ 50 values
60 dB input signal measures the response
Equivalent Input noise
measure the internal noise of the HA
- subtracting HFA FOG 50 from output measured when NO signal is being delivered to the aid
typically 25-30 dB SPL
Total Harmonic Distortion
measurement of signal distortion
determines if the output signal contains harmonic frequencies that were not present in the input signal
Total Harmonic Distortion
last 3 % below EIN
70 dB SPL @ 500 and 800
65 dB SPL @ 1600 HZ
% Total Harmonic Distortion should be below ?
5-10%
high distortion levels good indication device is failing sent it in for repair!
Induction coil/telecoil measurements
compares telecoil output to microphones reference test gain output
(ensure output from these two transducers is the same)
induction coil/telecoil measurements identify if
telecoils sensitivity provides greater output in the horizontal or vertical position
Telecoil Magnetic Field Simulator (TEST)
electromagnetic signal emitted from (T)
what is SPLITS
sound pressure level for an inductive simulator
output measurement of TMFS signal
SPLITS shows
TCOIL output
RSETS?
relative simulated equivalent telephone sensitivity
RSETS if difference between
SPLITS output and microphone output
a positive RSETS indicates ?
telecoil output is louder than the microphone output
What will user do to HA if + RSETS
lower the HA volume when telecoil is activated
a neagtive RSETS indicates?
telecoil output is softer than the microphone output
What will user need to do to HA if (-) RSETS
raise the HA volume when telecoil is activated
SPLIV
output compared to microphone in vertical position
LOOPED
VENT:
@ 500 HZ
50-60dB loss
.5 to no vent
VENT:
@ 500 HZ
40-49 dB loss
1-2mm
VENT:
@ 500 Hz
30-39
2-3mm or power dome
VENT:
@ 500 Hz
20-29 dB loss
3-3.5 mm or closed dome
VENT:
<20 db to 1.5k HZ
open dome
Tubing:
a change to the internal dimeter will change?
the device output and frequency response
Tubing:
#12
thicker and bigger opening
Tubing
#13
Smaller opening
Tubing= smaller diameter of inner tube =
attenuation of HF signals
Tubing = thick wall tube is used to reduce
vibration
reduces feedback
open dome coupler
appropriate for HF loss
- normal hearing til 1500 Hz
<20 dB to 1.5khz
closed or tulip dome
some mid frequency amplification
hearing thresholds better than 40 dB HL below 1khz
20-29 dB loss @ 500
power(double) dome coupler
provides some amplification to mid and low frequencies
- hearing thresholds better than 40 dB below 1 khz
30-39 dB loss at 500
