AE1 Test 3 Flashcards
What is REVERBERATION?
It’s the persistence of a signal in the form of reflected waves within an acoustic space, that continues after the original sound has ceased.
What is the function of REVERB?
To give a psychoacoustic sense of the space, of its size and its material composition.
Which type of mics work using electrostatic induction?
Condenser mics.
Which type of mics work using electromagnetic induction?
Dynamic and ribbon mics.
What are the components of a condenser mic?
Two capacitor plates. One called the diaphragm, made of a very light material and another called the back plate. All of it inside the diaphragm capsule.
How does a condenser mic work?
Via the electrostatic principle.
The SPL causes the diaphragm to move relative to the back plate causing the a change in the capacitance.
Why is the diaphragm gold plated?
To facilitate conduction while preventing rust.
How does a dynamic mic work?
Via electromagnetic induction.
How does a ribbon mic work?
Via electromagnetic induction.
What are the components of a ribbon mic?
A corrugated aluminum ribbon between two neodymium magnets.
What are the components of a dynamic mic?
A diaphragm attached to a coil positioned in the magnetic field of a magnet.
How do you avoid short-circuiting condenser mics?
By making all the connections first and then turning phantom power on.
How do you buy matched-pair microphones? And what can you use them for?
You must get two mics with sequential serial numbers.
You can use matched-pair mics for recording drums or any type of stereo miking.
What is the proximity effect?
It’s the artificial enhancement of low frequencies the closer the source is to the microphone.
What is transient response?
How easily a mic’s diaphragm is set into motion.
What is bleed-through?
When an instrument is picked-up by another instrument’s microphone.
What solutions are there for dealing with bleed-through.
- 3 to 1 rule,
- Iso booths,
- Gobos,
- Polar pattern and mic placement,
- Overdubbing.
What is the surface rule for the studio?
25% absorptiveness, 25% diffussiveness, 50% reflectiveness.
What is flat response?
Unity gain, 0dB of change.
What can you use omnidirectional mics for?
Recording ambient sound, choirs, as lapel mics…
What are the different stereo micing techniques? Explain each technique, their drawbacks and/or advantages.
- Spaced pair: two mics a few feet to more than 30ft apart.
Drawback: strong potential for phase discrepancies, specially for mono. - X/Y: two coincident mics facing each other at an angle between 90* and 135*.
Advantage: no phase problems. - M/S: two coincident mics, a cardioid (mid) facing the source and a bidirectional with the null facing the source.
Advantage: absolute mono compatibility. - Decca tree: three mics, two 3ft apart from each other and a third 1,5ft in front (mid). Mounted on a tall boom pole. Favored for orchestral situations.
What do a TRS cable’s initials stand for? What’s its main feature?
Tip - Ring - Sleeve.
It’s a balanced cable, which means it cancels out noise.
What is a TS cable?
An unbalanced 1/4” cable, used mainly for instruments like electric guitars.
What does a D.I. box do?
It converts an unbalanced signal into a balanced one.
What are the four-distances miking techniques?
- Close miking: source (excludes ambient sound).
- Distant miking: source + ambient sound.
- Accent miking: to emphasize an instrument within an ensemble.
- Ambient miking: room or ambient sound is equally or more prominent than the direct sound.
What is a “clip” in Pro Tools?
A piece of audio.
Describe the 4 edit modes in Pro Tools. What are their hotkeys?
F1 = Shuffle: affects everything to the right of the edit. F2 = Slip: lets you freely move things around w/o affecting the rest automatically. F3 = Spot: always queries you about the exact spot where you want to move the audio to. F4 = Grid: Lets you snap audio to certain time divisions.
Hotkey for: Closing the current session
Cmd + Shift + W
Hotkey for: Closing all plug-in windows
Cmd + Opt + W
Hotkeys for: Recording
Cmd + Space Bar F12 KP3 Button on screen Button on console
Name the differences between analog and digital recording.
- Expensive / Cheap
- Tape is expensive to ship / Can send information online
- Contiguous signal (always on) / Fixed measurements throughout time (on and off)
- Linear access / Random access
- Complicated edit / Simple
- Complicated duplication process / Extremely simple
- 2” tape = 16 tracks / Unlimited tracks
- Volatile
- Problems when recording more than once / Can record over and over
Average CD storage capacity:
4.38Gb
Define “sample rate”.
How many times per second the voltage is measured.
Define “bit depth”.
The number of bits of information in each sample. It directly corresponds to the resolution of each sample.
What are a CD’s sample rate, bit depth and dynamic range?
44,100Hz, 16 bits and 96dBFS
What are a DVD’s sample rate, bit depth and dynamic range?
48,000Hz 24 bits and 144dBFS
To how many dBs of dynamic range does 1 bit correspond to?
6dBFS
Explain the NYQUIST Theorem.
The sample rate must be equal to at least twice the highest frequency to be recorded.
What does a NYQUIST Filter do?
It filters out sounds above 20,000Hz.
IOW, when a LP Filter is set to 20KHz, it’s a NYQUIST Filter.
What does a DAW do?
It records a map of voltages.
What is “quantizing”?
Rounding up or down the voltage to the closest bit depth number.
What is “dithering”? When should you use it?
Adding a small amount of noise into the conversion process to improve the signal’s performance when down sampling, to prevent quantization distortion. It should be used before mastering.
Draw a sound processing chain from sound source to speakers and indicate which components are transducers with an “x”.
SPL - microphone x - mic pre - interface (NYQUIST Filter - Sample & Hold - A/D x) - DAW - D/A x- powered amp - speaker x
What does the “sample & hold” function of an interface do?
Makes a measurement of voltage and holds it for 1/48,000th of a second before taking another sample.
What does a transducer do?
It transforms one form of energy into another.
What is Interleaved Error Correction?
Spreading the data around so that errors are more uniformly distributed, lessening the probability of information dropouts.
What’s the 3 drawbacks of using a higher resolution for recording?
It lowers your track count, relative processing power and makes bigger files.
What is the ideal gain level for recording?
Between -12dBFS and -20dBFS
Name all the digital audio transmission standards, the number of channels they can transmit and the cable they use.
- S/PDIF, 2ch, RCA
- AES/EBU, 2ch, XLR
- ADAT Lighpipe, 8ch, optical cables
- TDIF, 8ch, 25 pin D-sub
- MADI, 56ch, Coax or fiber-optic
What do we need so that signals between devices stay in sync?
A wordclock.
What is the relation between bits and bytes?
8 bits = 1 byte
What is the relation between bytes and words?
8 bytes = 1 word
Explain a square wave.
A series of ONs and OFFs of equal length and at a regular frequency.
What is the relationship between a pulse wave and a square wave?
A square wave is a pulse wave but a pulse wave is not necessarily a square wave.
What can cause a bad signal between devices?
- RF or noise: never lay an audio cables on top of electrical cables.
- Defective connectors
- Dirty connectors
- Too long (unbalanced) cables
What is a wordclock?
A word clock is what tells a A/D or D/A converter when to take the sample. It fires an impulse to the converter 44.1k (or 48k, or 96k, etc) times per second. The reliability of this clock, how evenly spaced those pulses are, determines the accuracy of the conversion process.
If you have digital connections in your studio (S/PDif, lightpipe, etc), you MUST have a single clock source. If multiple devices are each trying to be the master clock, you will probably experience pops, clicks, or sometimes chirps in your audio. The solution is usually to make sure that you only have one master clock, and that all slave units are getting a clean clocking signal.
What is SMPTE Timecode?
SMPTE timecode is a set of standards to label individual frames of video and film with a time code defined by the Society of Motion Picture and Television Engineers.
Timecodes are added to video, film and audio material and have also been adapted to synchronize music. They provide a time reference for editing, synchronization and identification. Timecode is a form of media metadata. This made modern videotape editing possible, and led eventually to the creation of non-linear editing systems.
What is “data interleaving”?
It’s a form of error correction. It works by spreading the data around so that errors are more uniformly distributed, lessening the probability of information dropouts.
An audio interleaved file…
…contains 2 or more audio channels.
What is a master device as opposed to a slave device?
The device that puts out the sync signal all the slave devices sync to.
Explain “daisychaining”.
The output of a device goes into the input of another and so on.
What is a “distribution box”?
The better alternative to daisychaining. A centralized clock.
In which order should you turn on your devices?
- Computer. Let it go idle.
- Other devices.
- Speakers.
- Phantom power.
In which order should you trun off your devices?
- Phantom power.
- Speakers.
- Other devices.
- Computer.
What do the F keys do?
F1 = Shuffle F2 = Slip F3 = Spot F4 = Grid F5 = Zoom tool F6 = Trim tool F7 = Selector tool F8 = Grabber tool F9 = Scrubber tool F10 = Pencil tool F11 = Wait-for-MIDI trigger F12 = Record F13 = Client appeaser
