Digital Signal Processing in Hearing Aids Flashcards

In a DSP hearing aid, what is the 'equivalent input noise' (EIN) specification used to evaluate?

Answer: The noise floor introduced by the hearing aid's own microphone and electronics

EIN measures the self-noise of the hearing aid system referenced to the input, indicating how quiet the device is when no sound is present; lower EIN values are better.

Which hearing aid feature uses DSP to compare microphone signals and identify the location of a speaking talker?

Answer: Spatial noise reduction / beamsteering

Spatial noise reduction algorithms analyze inter-microphone level and time differences to identify where speech is coming from and enhance that direction while suppressing other directions.

What is 'harmonic distortion' in the context of hearing aid amplifier performance?

Answer: The creation of unwanted frequency components at multiples of the original signal frequency

Total harmonic distortion (THD) measures unwanted harmonics added by the amplifier to the original signal; high THD results in a distorted, unclear sound quality.

A clinician is adjusting the 'compression knee-point' (threshold kneepoint) in fitting software. Lowering the kneepoint will:

Answer: Cause compression to engage at softer input levels, amplifying more of the dynamic range

A lower compression threshold (kneepoint) means the compressor activates at softer sounds, applying gain reduction across a wider range of input levels.

What technology allows modern hearing aids to stream audio directly from smartphones without an intermediate streaming device?

Answer: Made for iPhone (MFi) / ASHA (Audio Streaming for Hearing Aids) Bluetooth protocols

Apple's MFi protocol and Google's ASHA standard enable direct Bluetooth audio streaming from smartphones to compatible hearing aids without a neck-worn relay device.

In digital hearing aids, 'datalogging' refers to:

Answer: Recording environmental statistics and usage data stored in the hearing aid's memory

Datalogging captures information about how the patient uses the hearing aid — program use, volume adjustments, hours worn, and acoustic environments — to inform future fitting adjustments.

Which of the following is a key difference between 'linear amplification' and 'non-linear amplification' in DSP hearing aids?

Answer: Linear amplification applies the same gain regardless of input level; non-linear varies gain based on input level

Linear amplifiers apply a fixed gain to all input levels, while non-linear (compressive) amplifiers vary the amount of gain depending on how loud the incoming sound is.