Introduction and History Flashcards
What is dB input?
Sounds from the environment coming into the device
What is dB gain?
The amount of amplification added to the input
What is the dB output?
The intensity of the signal that is delivered to the ear canal
What are the dB values for soft, moderate, and loud?
Soft: 50 dB
Moderate: 65 dB
Loud: 80 dB
Will dB always be dB SPL in this class?
Yes
Is audiometric data converted from HL to SPL before the amplification fit?
Yes
The conversion is done based on the size of an average adult ear
What are the 5 hearing aid eras?
Acoustic, carbon, vacuum tube, transistor, and microelectronic/digital
When did the acoustic era take place?
From the 13th to 19th century
Due to the fact that electronic amplification didn’t exist
What is the acoustic horn principle?
The intensity of an acoustic signal changes as it travels through a horn
Horns amplify sounds when waves are reflected into a progressively narrower area
Increases the sound pressure level that reaches the ear
What else can horns do besides just amplifying the sound pressure level?
It can increase directionality (you can point the horn in the direction you want)
Do horns cause sound distortion?
Yes
Are all frequencies equally amplified with a horn?
Yes
What was considered the first acoustic horn?
Hand cupping
How much gain did hand cupping provide?
10 to 15 dB of gain to the input signal in mid to high frequencies
Increases gain of signals arriving from the front and attenuates signals arriving from the rear
Does the length and size of the horns opening determine the final output intensity?
Yes
Increased length of the horn increased the SPL energy transferred to the ear
Wider openings collect more sound
Does a combination of increased length and wider openings maximize the gain added to the input signal?
Yes
What do frequency response curves compare?
They compare the intensity of the input signal to either the added gain, or the final output of a device
What frequencies receive a lot of gain with a horn?
Lows
What does a horn sound like?
It amplifies the sound, but it doesn’t really make it clearer
What was the carbon era?
It refers to a time when the first electric hearing aids used a carbon microphone and a receiver
1902
What did carbon microphones convert acoustic signals into?
Analog electric signals
From the analog electric signal, what did the receiver on the carbon hearing aid do?
It converted the analog electric signal back to an acoustic signal
Did carbon hearing aids have amplifiers to add gain to the acoustic input signals?
No
“Resonance reflectors” were positioned behind the mic and added 5 to 10 dB SPL of gain to the input signal between 1000 and 3500 Hz
Mics were stacked on top of each other for more gain too
What was the vacuum tube era?
Vacuum tube amplifier was invented
Added gain to increase the amplitude of the analog electric signal
1920
How many batteries did the early vacuum tube amplifiers use?
2
One to warm the filament
One to amplify sound
When did vacuum tube amplifiers reduce in size so they could fit inside a pocket?
1940
What frequency did vacuum tube amplifiers mainly amplify?
2000 Hz
Helped people with hearing loss hear soft consonants better
What is the transistor era?
Small transistors and resistors replaced vacuum tubes in the 1950s
What is a transistor?
It is an electrical component used to increase current flow of electronic signals (increases amplitude)
What is a resistor?
It is an electrical component used to add or remove resistant resistance to the flow of electrical current (modifies frequency response or output)
What is used today instead of transistors and resistors?
Integrated circuits
Combines multiple transistors and resistors
Very small
What is a potentiometer?
A small resistors control used to modify the output signal in early analog hearing aids
Manipulated the output signal, the frequency gain response, the amount of gain added, and the compression ratio
