Electrical Systems & Wiring Flashcards

According to ANSI S3.6, audiometer calibration checks should be performed at minimum:

Answer: Annually by a certified calibration laboratory, with daily biologic checks

ANSI S3.6 requires formal electroacoustic calibration annually while daily biologic listening checks by the clinician verify that no major changes have occurred.

Which piece of equipment is used to verify the output level of a bone conduction oscillator during audiometer calibration?

Answer: A mechanical coupler (artificial mastoid) with a force-measuring transducer

An artificial mastoid (mechanical coupler) simulates the impedance of the human skull and measures vibratory force output of the bone conduction oscillator in dB re: 1 μN.

Electromagnetic interference (EMI) from a fluorescent lighting ballast in a test room is BEST mitigated by:

Answer: Installing electronic ballasts and shielding lighting wiring away from electrode cables

Electronic ballasts operate at much higher frequencies (>20 kHz) producing less interference in the auditory range, and separating wiring reduces capacitive coupling of EMI into electrode leads.

The leakage current limit for Type BF (body floating) patient-applied electrodes used in auditory evoked potential testing is:

Answer: 10 μA

IEC 60601-1 specifies a maximum patient leakage current of 10 μA for Type BF applied parts under normal conditions, protecting patients from microshock.

When using insert earphones, an acoustic tube that is kinked or partially occluded will MOST likely cause:

Answer: Attenuation of high-frequency output and possible standing wave artifacts

A compromised acoustic tube acts as a low-pass filter, reducing high-frequency energy transmission and potentially creating resonances that alter the calibrated frequency response.

Radio-frequency interference (RFI) from a nearby cell phone can contaminate electrophysiological recordings primarily through:

Answer: Capacitive coupling into unshielded electrode leads acting as antennas

Unshielded or improperly shielded electrode cables can act as antennas, capacitively coupling RF energy from nearby transmitters into the differential amplifier inputs.

The purpose of a preamplifier positioned close to the recording electrodes in an ABR system is to:

Answer: Amplify the microvolt-level signal before cable-length noise is introduced

Amplifying the signal close to the source (before the long cable run) improves the signal-to-noise ratio because cable-induced noise added after preamplification is relatively insignificant.