Capturing Sound

Question 1

Transduction

Answer 1

changing of one type of energy to another

Question 2

microphone definition

Answer 2

a transducer that converts acoustic energy into electrical energy

Question 3

loudspeaker definition

Answer 3

a transducer that converts the electrical energy into acoustic energy

Question 4

Sequence of an Audio Signal Pathway (6)

Answer 4

• A sound source creates sound wave vibrations in the air
• The vibrations of the sound waves are picked up by a microphone
• microphone converts the vibrations into an electrical signal
• The electrical signal is processed
• The signal is sent to an output device
• An output device transduces the electrical signal into sound waves

Question 5

Dynamic Microphone Construction (3)

Answer 5

• Coil of wire is attached to a diaphragm and placed in a permanent magnetic field
• As the diaphragm and coil assembly moves, it cuts across the magnetic lines of flux of the magnetic field, inducing a voltage onto the coil of wire
• voltage induced into the coil is proportional to the sound pressure and produces an electrical audio signal

Question 6

Mic Level

Answer 6

a very low level signal only a few millivolts of electrical energy

Question 7

Dynamic microphone characteristics (3)

Answer 7

• produce mic level signal
• do not require power
• economical, durable, and will handle high sound pressure levels

Question 8

capacitor (3)

Answer 8

• two oppositely charged (polarized) conductors separated by an insulator
• an electric field exists between the two conductors
• The amount of potential charge (voltage) that is stored between the conductors will change depending upon the distance between the conductors, the surface area of the conductors, and the dielectric strength of the insulating material between the two conductors

Question 9

Condenser microphone construction (6)

Answer 9

• a conductive diaphragm and a conductive backplate
• Air is used as the insulator to separate the diaphragm and backplate
• sound waves cause the diaphragm to move back and forth
• As the distance changes, the amount of charge stored between the diaphragm and backplate changes
• This change in capacitance produces an electrical audio signal at the output of the capsule
• a condenser microphone includes a preamplifier that amplifies the signal to a microphone level signal

Question 10

phantom power

Answer 10

Voltage sent to a condenser microphone between about 15V and 48 V

Question 11

Electret Microphones (3)

Answer 11

• a type of condenser microphone
• It has prepolarized material, called “electret,” which is applied to the microphone’s diaphragm or backplate
• This permanent charge eliminates the need for the higher voltage required for powering the typical condenser microphone, so it can be powered using small batteries and normal phantom power

Question 12

Microphone Physical Design (6)

Answer 12

• Handheld
• Lavalier
• Gooseneck
• Surface Mount
• Integrated/Array
• Shotgun

Question 13

Handheld Microphones (2)

Answer 13

• used mainly for speech or singing

- includes internal shock mounting to reduce handling noise

Question 14

Boundary Microphones

Answer 14

mounted directly against a hard surface

Question 15

Integrated/Array Microphones

Answer 15

include multiple microphone elements and signal processing for applications like web conferencing

Question 16

Gooseneck Microphones

Answer 16

used most often on lecterns and conference tables

Question 17

Shotgun Microphones

Answer 17

named for their physical shape, as well as their long and narrow polar pattern

Question 18

Wearable Microphones

Answer 18

• lavalier is attached directly to clothing

- head microphone is a microphone that is attached to a small, thin boom and fitted around the ear

Question 19

Microphone Polar Patterns (4)

Answer 19

Omnidirectional
Cardioid
Supercardioid
Bi-directional

Question 20

Omnidirectional

Answer 20

Sound pickup uniform in all directions

Question 21

Cardioid

Answer 21

Pickup from front only. Rejects sound coming from side, with most rejection at rear

Question 22

Supercardioid

Answer 22

Narrower pickup than cardioids and greater rejection of ambient sound but has some pickup directly at rear

Question 23

Bi-directional

Answer 23

Pickup equal in opposite directions with little or no pickup from sides

Question 24

Microphone Sensitivity (2)

Answer 24

• If you expose two different types of microphones to an identical sound input level, a more sensitive microphone provides a higher electrical output than a less sensitive microphone.
• Condenser microphones are usually more sensitive than dynamic microphones.

Question 25

Microphone Sensitivity Specifications

Answer 25

An example of a sensitivity specification may look like this: -54.5 dBV/Pa 1 Pa = 94 dB SPL. “Pa” refers to the Pascal and it is a unit of pressure. 1 Pascal is the equivalent of 94 dB SPL. In this example, if you were to put 94 dB SPL into the microphone, you would realize a -54.5 dBV electrical output signal.

Question 26

Microphone Frequency Response

Answer 26

defines the microphone’s electrical output level over the audible frequency spectrum

Question 27

Microphone Impedance (3)

Answer 27

- Impedance is the total opposition to current flow in an AC circuit. - Microphones can fall into two categories based upon output impedance: Low impedance – 200 ohms or less (some as high as 600 ohms) High impedance – More than 25,000 ohms. - Professional microphones are low impedance microphones.

Question 28

Wireless Microphones

Answer 28

use RF transmission in place of a microphone cable

Question 29

Professional microphone cables

Answer 29

shielded twisted pair

Question 30

shielded twisted pair

Answer 30

two insulated wires twisted with a shield wrapped around them

Question 31

Audio Signal Levels (3)

Answer 31

Mic Level Line Level Loudspeaker Level

Question 32

Mic Level Voltage

Answer 32

0.001 - 0.003 volts

Question 33

Line Level (Professional) Voltage

Answer 33

1.23 volts

Question 34

Line Level (Consumer) Voltage

Answer 34

0.316 volts

Question 35

Loudspeaker Level Voltage

Answer 35

4 volts or more

Question 36

Common Signal Level Adjustments (3)

Answer 36

Gain Attenuation Unity Gain

Question 37

Gain

Answer 37

the electronic amplification of a signal.

Question 38

Attenuation

Answer 38

signal level out is less than the signal in

Question 39

Unity Gain

Answer 39

no change in gain