Hearing Aid Dispenser Exam UPDATED
ACTUAL Questions and CORRECT
Answers
Frequency - CORRECT ANSWER- - How many times per second a sound wave alternates
pressure
- Measured in Hz or kHz
Period - CORRECT ANSWER- - Time taken for a repetitive sound wave to finish one cycle.
- = 1/f
Phase - CORRECT ANSWER- - Describes the timing of a sound
Two waves are out of phase when... - CORRECT ANSWER- there waveforms are
proportional, but all frequencies have a 180 degrees phase shift (opposite polarity).
Wavelength - CORRECT ANSWER- The distance a sound wave travels in one period.
Sound Pressure Level - CORRECT ANSWER- - Number of dB by which any sound
pressure exceeds the reference (2x10^-5 pa).
When pressure doubles, how much is added? - CORRECT ANSWER- 6 dB
When pressure increases 10 times, the SPL increases by... - CORRECT ANSWER- 20 dB
An octave is... - CORRECT ANSWER- a doubling of frequency
, Fourier Analysis - CORRECT ANSWER- A mathematical procedure by which any signal
can be separated into component sine waves at different frequencies. Combining these sine
waves will reproduce the original signal.
Gain is calculated by... - CORRECT ANSWER- Output level minus input level
Is compression linear or non-linear - CORRECT ANSWER- Non-linear
Name the essential parts of a HA - CORRECT ANSWER- - One or more mics to convert
sound into an electrical signal
- An amplifier to increase the strength of the electrical signal
- A mini loudspeaker (receiver) to turn the electricity back to sound
- Means of coupling the sound source to the ear canal.
- A battery
How do directional microphones work? - CORRECT ANSWER- - Suppress noise coming
from on mic/port while retaining good sensitivity to the sound coming from another direction.
Name some sensitivity pattern of a HA with directional mics enabled - CORRECT ANSWER-
Cardioid (has a heart shaped pattern), super cardiod, hyper cardiod, figure 8
Why is distortion bad? - CORRECT ANSWER- Degrades intelligibility
What are distortion products? - CORRECT ANSWER- - Areas that have been peak clipped
from the original sound signal.
Total Harmonic Distortion (THD) - CORRECT ANSWER- - Measurement of the harmonic
distortion present; Defined as the ratio of the sum of the powers of all harmonic components to
the power of the fundamental frequency.
ACTUAL Questions and CORRECT
Answers
Frequency - CORRECT ANSWER- - How many times per second a sound wave alternates
pressure
- Measured in Hz or kHz
Period - CORRECT ANSWER- - Time taken for a repetitive sound wave to finish one cycle.
- = 1/f
Phase - CORRECT ANSWER- - Describes the timing of a sound
Two waves are out of phase when... - CORRECT ANSWER- there waveforms are
proportional, but all frequencies have a 180 degrees phase shift (opposite polarity).
Wavelength - CORRECT ANSWER- The distance a sound wave travels in one period.
Sound Pressure Level - CORRECT ANSWER- - Number of dB by which any sound
pressure exceeds the reference (2x10^-5 pa).
When pressure doubles, how much is added? - CORRECT ANSWER- 6 dB
When pressure increases 10 times, the SPL increases by... - CORRECT ANSWER- 20 dB
An octave is... - CORRECT ANSWER- a doubling of frequency
, Fourier Analysis - CORRECT ANSWER- A mathematical procedure by which any signal
can be separated into component sine waves at different frequencies. Combining these sine
waves will reproduce the original signal.
Gain is calculated by... - CORRECT ANSWER- Output level minus input level
Is compression linear or non-linear - CORRECT ANSWER- Non-linear
Name the essential parts of a HA - CORRECT ANSWER- - One or more mics to convert
sound into an electrical signal
- An amplifier to increase the strength of the electrical signal
- A mini loudspeaker (receiver) to turn the electricity back to sound
- Means of coupling the sound source to the ear canal.
- A battery
How do directional microphones work? - CORRECT ANSWER- - Suppress noise coming
from on mic/port while retaining good sensitivity to the sound coming from another direction.
Name some sensitivity pattern of a HA with directional mics enabled - CORRECT ANSWER-
Cardioid (has a heart shaped pattern), super cardiod, hyper cardiod, figure 8
Why is distortion bad? - CORRECT ANSWER- Degrades intelligibility
What are distortion products? - CORRECT ANSWER- - Areas that have been peak clipped
from the original sound signal.
Total Harmonic Distortion (THD) - CORRECT ANSWER- - Measurement of the harmonic
distortion present; Defined as the ratio of the sum of the powers of all harmonic components to
the power of the fundamental frequency.
