Introduction and History

Question 1

What is dB input?

Answer 1

Sounds from the environment coming into the device

Question 2

What is dB gain?

Answer 2

The amount of amplification added to the input

Question 3

What is the dB output?

Answer 3

The intensity of the signal that is delivered to the ear canal

Question 4

What are the dB values for soft, moderate, and loud?

Answer 4

Soft: 50 dB
Moderate: 65 dB
Loud: 80 dB

Question 5

Will dB always be dB SPL in this class?

Answer 5

Yes

Question 6

Is audiometric data converted from HL to SPL before the amplification fit?

Answer 6

Yes
The conversion is done based on the size of an average adult ear

Question 7

What are the 5 hearing aid eras?

Answer 7

Acoustic, carbon, vacuum tube, transistor, and microelectronic/digital

Question 8

When did the acoustic era take place?

Answer 8

From the 13th to 19th century
Due to the fact that electronic amplification didn’t exist

Question 9

What is the acoustic horn principle?

Answer 9

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

Question 10

What else can horns do besides just amplifying the sound pressure level?

Answer 10

It can increase directionality (you can point the horn in the direction you want)

Question 11

Do horns cause sound distortion?

Answer 11

Yes

Question 12

Are all frequencies equally amplified with a horn?

Answer 12

Yes

Question 13

What was considered the first acoustic horn?

Answer 13

Hand cupping

Question 14

How much gain did hand cupping provide?

Answer 14

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

Question 15

Does the length and size of the horns opening determine the final output intensity?

Answer 15

Yes
Increased length of the horn increased the SPL energy transferred to the ear
Wider openings collect more sound

Question 16

Does a combination of increased length and wider openings maximize the gain added to the input signal?

Answer 16

Yes

Question 17

What do frequency response curves compare?

Answer 17

They compare the intensity of the input signal to either the added gain, or the final output of a device

Question 18

What frequencies receive a lot of gain with a horn?

Answer 18

Lows

Question 19

What does a horn sound like?

Answer 19

It amplifies the sound, but it doesn’t really make it clearer

Question 20

What was the carbon era?

Answer 20

It refers to a time when the first electric hearing aids used a carbon microphone and a receiver
1902

Question 21

What did carbon microphones convert acoustic signals into?

Answer 21

Analog electric signals

Question 22

From the analog electric signal, what did the receiver on the carbon hearing aid do?

Answer 22

It converted the analog electric signal back to an acoustic signal

Question 23

Did carbon hearing aids have amplifiers to add gain to the acoustic input signals?

Answer 23

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

Question 24

What was the vacuum tube era?

Answer 24

Vacuum tube amplifier was invented
Added gain to increase the amplitude of the analog electric signal
1920

Question 25

How many batteries did the early vacuum tube amplifiers use?

Answer 25

2
One to warm the filament
One to amplify sound

Question 26

When did vacuum tube amplifiers reduce in size so they could fit inside a pocket?

Answer 26

1940

Question 27

What frequency did vacuum tube amplifiers mainly amplify?

Answer 27

2000 Hz
Helped people with hearing loss hear soft consonants better

Question 28

What is the transistor era?

Answer 28

Small transistors and resistors replaced vacuum tubes in the 1950s

Question 29

What is a transistor?

Answer 29

It is an electrical component used to increase current flow of electronic signals (increases amplitude)

Question 30

What is a resistor?

Answer 30

It is an electrical component used to add or remove resistant resistance to the flow of electrical current (modifies frequency response or output)

Question 31

What is used today instead of transistors and resistors?

Answer 31

Integrated circuits
Combines multiple transistors and resistors
Very small

Question 32

What is a potentiometer?

Answer 32

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