Audio Capture Portfolio

Question 1

Pressure microphone

Answer 1

has one side of its diaphragm open to external sound waves and the other side closed in a fixed pressure system. Pressure mics are omnidirectional and exhibit no proximity effect, and are fairly resistant to plosives.

Question 2

Pressure-gradient microphone

Answer 2

has both sides of its diaphragm open to sound waves (at least partially). Pressure-gradient capsules are found in all directional mics (including ribbon and multi-directional condensers).

Question 3

What is a Microphone?

Answer 3

a device that converts acoustic energy into electrical energy.

Question 4

Dynamic Microphone

Answer 4

Has a coil glued to its rear membrane with a strong magnet surrounding it. When sound waves hit the microphone, the membrane moves to the rhythm of the sound waves, along with the coil. The relative movement of the coil within its magnetic gap induces a small signal voltage.

Question 5

Dynamic Ribbon Microphone

Answer 5

Instead of having a membrane and a coil, a ribbon transducer uses a narrow strip of extremely thin aluminum foil. Sound waves coming from the sides do not set the ribbon in motion. This pickup pattern is called figure-8.

Question 6

Condenser/Capacitor microphones

Answer 6

is two metal plates in close proximity. The closer they are, the higher the capacitance. When sound waves hit the diaphragm the distance between the two capacitor plates changes. As a result, the capacitance changes to the rhythm of the sound waves. Therefore converting sound into an electrical signal.

Question 7

Condenser microphone capsule

Answer 7

consists of a thin membrane in close proximity to a solid metal plate. The membrane/diaphragm must be electrically conductive, at least on its surface. The most common material is gold-sputtered mylar, but older models employ an extremely thin metal foil.

Question 8

Condenser microphones history

Answer 8

Early 1920 Neumann microphones required external PSU boxes for each individual mic along with a dedicated multipin cable. When transistor technology took over in the late 1960s, Neumann instead powered Condenser microphones through P48 phantom power.

Question 9

tube condenser microphones

Answer 9

require an external power supply, because tubes consume more energy than phantom power is able to provide.

Question 10

Proximity Effect

Answer 10

is a phenomenon; found especially in bass heavy sources, that leads to an increase in low frequency/bass as you move the mic closer to the source. This can be problematic or useful, depending on your desired outcome.

Question 11

Proximity Effect example

Answer 11

the E-string on a guitar is around 80 Hz often sounding very “boomy” when the mic is placed too close. But for dedicated bass instruments such as a kick drum/bass guitar, the proximity effect can bring out low frequency content.

Question 12

Proximity Effect microphones

Answer 12

Most apparent on figure-8’s, followed by cardioids. Omnidirectional mics have no proximity effect whatsoever.

Question 13

Close mic placing

Answer 13

Creates an intimate, tight & present capture of the sound source, whilst minimizing ambient noise.

Question 14

Spill

Answer 14

Unintentionally picking up external instrument audio. Can cause ‘level’ and ‘phase cancellation’ issues. The 3:1 Distance Rule retains phase integrity. Booths or acoustic barriers can help too.

Question 15

Ambient Mic. Placement

Answer 15

Combining a close mic and ‘room/ambient’ mics we can capture both the direct sound source and some of the rooms acoustics.

Question 16

Spaced Pair (AB)

Answer 16

2 identical mics placed at the same height, between 2-30 feet apart. This can cause phase cancellation/comb filtering because of time delay between microphones and can be especially problematic in the mixing process, for instance when panned or placed in mono.

Question 17

comb filtering

Answer 17

is a phenomenon that happens when two of the same sounds arrive at the listener’s ears with a very small delay between the two signals; sonically sounding ‘tinny’ and ‘robotic.

Question 18

X/Y Pair (Co-Incident)

Answer 18

2 identical mics, facing each other at an angle between 90 & 135 degrees, placed at the same height and positioned as close together without touching. Often better stereo imaging than Spaced Pairs and Cardioid Pattern works best.

Question 19

ORTF Technique

Answer 19

is a stereo technique in which two cardioid microphones are spread 110 degrees with their capsules positioned 17cm’s apart. Often using Cardiod or Omni Polar pattern.

Question 20

Glyn Johns technique.

Answer 20

4 mics:
AKG D112 (dynamic)=bass drum
Sure Sm57 (dynamic)=snare
2 Neumann U87’s (large diaphragm condenser)=overheads

Question 21

Piano

Answer 21

Range is 27.5 Hz (A0) to 4186 Hz (C8). Every grand piano’s string follows a similar pattern. The best bass tones come from longer/thinner strings, with its strings crossing over the higher note string, allowing for greater string length. Best bass = concert grand piano > baby grand/upright.

Question 22

Grand piano

Answer 22

Often used in classical music. Uses additional microphones what aren’t as closely placed, and may cause spill.

Question 23

Upright Piano

Answer 23

smaller than a grand piano. Often used in jazz, blues, and rock music, as they have a brighter and more percussive sound. Recorded with exposed string one mic near the bass strings and one near the treble strings about 8 inches away. Tune mic angle to reduce boomy/muddy timbre.

Question 24

Mid/Side decoding

Answer 24

Encoding: R/L are summed into mono, and “side” is the leftover subtraction of R/L.
Combining: Mono & Side are combined into a stereo signal. Left = Mid + Side, Right = Mid - Side.
Decoding: the stereo signal is split back into the Mid/Side signals” Mid = (Left + Right) ÷ 2, Side = (Right - Left) ÷ 2.

Question 25

M/S recording technique

Answer 25

Mid: 1 cardioid/directional mic facing sound source (converted to mono)
Side: 1 figure 8/bi-directional mic placed at 90º to mid microphone (panned hard left+right with right phase inversed 180).

Question 26

3:1 Rule

Answer 26

If one mic is 1 foot from a source, the second mic should be placed no closer than 3 feet from the source.