Midterm Flashcards
(59 cards)
what does a basic hearing aid do?
- collect sounds from the environment
- transduce the sounds (acoustic signals) into analogous electrical signals
- modify the electrical signals per the instructions of the audiologist (frequency shaping & amplification)
- transduce modified electrical signals into analogous & modified acoustic signals
- deliver modified acoustic signals (sounds) to the TM
transducer
a device that converts energy from one form to another
signal
- conveys information about the behavior or attributes of some phenomenon
- usually a transducer converts ____ in one form of energy to a ____ in another
- has energy and information
microphone
- device that converts sound waves into analogous electrical waves (sound energy to electrical energy)
- the diaphragm movement modulates an electrical current
condenser microphones
- electrostatic mic
- capacitor mic
- the diaphragm changes the capacitance btwn itself and a metal plate, both acting as electrodes
- widely used electret mic has a charged dielectric btwn the electrodes that generate voltage
electret microphone
type of electrostatic capacitor based microphone which eliminates the need for polarizing power supply by using a permanently charged material
receiver
changes the amplified electronic signal into acoustic signal
amplifier
- device that accepts a small signal and outputs a larger signal that generally matches the waveform characteristics of the input
- take power from the battery and transfer it to the _____ output in a manner controlled by the input signal
transistors
- generate amplification
- electrical switches that amplify sound
class A amplifier
- conducts current throughout the entire cycle (360 degrees)
- most inefficient and is used in low power applications as well as in very high end stereo
class B amplifier
current flows only 180 degrees for half the cycle or two transistors can be used in a push-pull fashion, each operating for 180 degrees.
- low end products
class AB amplifier
- combines A and B and current flows for 180-200 degrees
- most widely used in audio applications
class C amplifier
- operating for less than half of one wave cycle (100-150 degree)
- most efficient but not used for audio applications because of excessive distortion
peak clipping
when the input signal exceeds the amplifier capacity and produces distortion
hearing aid fundamental components
mic, amplifier, speaker (receiver), power supply (battery)
analog circuits; analogous
- representation of an object that resembles the original
- monitors conditions such as movement, temperature, and sound and converts them into _______ electronic or mechanical patterns
analog hearing aids
- turn voice vibrations into electrical vibrations of the same shape
- continuous signal
digital hearing aids
- breaks everything into numbers
batteries
generate electricity by putting two electrodes near an electrolyte
telecoil
a small coil of wire, usually around a ferrite rod, that produces a voltage when an alternating magnetic field flows through it
induction
process of an electrical current introducing a voltage in a coil
low pass
- high cut
- more gain to LF than HF sound (bass)
high pass
- low cut
- more gain to HF than LF sounds (trebble)
bandpass
- emphasize a defined range of frequencies
- cuts both lows and highs and preserves the mids
