Electrical Systems & Wiring Flashcards
7 cards from real ABA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems & Wiring flashcards as text
In an audiometer circuit, the attenuator is typically placed:
Answer: Between the signal generator and the power amplifier
Placing the attenuator between the oscillator and amplifier ensures that noise from the amplifier is not attenuated, but signal level control is achieved before amplification.
Impedance matching between an audiometer and an earphone transducer is important because:
Answer: It ensures maximum power transfer and prevents signal reflections
Maximum power transfer occurs when source and load impedances are matched, ensuring accurate and efficient delivery of the test signal to the transducer.
A capacitor in an audiometer circuit is used to block DC while passing AC signals primarily because:
Answer: Capacitive reactance decreases with increasing frequency allowing AC but blocking DC
Capacitive reactance (Xc = 1/2πfC) approaches infinity as frequency approaches zero (DC), effectively blocking DC while allowing AC signals to pass.
Which circuit element in a hearing aid output stage limits maximum acoustic output to protect residual hearing?
Answer: An automatic gain control (AGC) or output limiting circuit
AGC circuits and output limiters are specifically designed to prevent the hearing aid from exceeding prescribed maximum output levels (OSPL90).
In an electroacoustic analysis setup, a 2-cm³ coupler has a known acoustic impedance because it:
Answer: Provides a standardized reproducible cavity for consistent SPL measurements
The standardized volume of the 2-cm³ coupler provides a reproducible acoustic load, allowing consistent and comparable hearing aid output measurements across facilities.
When an audiometer's power supply filter capacitors degrade, the MOST likely symptom is:
Answer: Increased ripple noise superimposed on the test signal
Filter capacitors smooth the rectified AC supply; when they degrade, residual AC ripple passes through to the signal chain, adding noise to the output.
Ohm's law applied to the electrical equivalent circuit of the middle ear predicts that increasing the stiffness of the ossicular chain will:
Answer: Increase the capacitive reactance analog, reducing low-frequency energy transfer
In the electrical analogy, stiffness maps to capacitance; increased stiffness reduces compliance, raising capacitive reactance and impeding low-frequency sound transmission.