BPM202: Digital Music Production II - Quiz #1: Audio Interface

AUDIO INTERFACE

• Achieves an analog audio signal converted from analog electrical information into a method a computer can understand (DIGITAL)

  • CONTAINS 1 OR MORE OF:

    1. ADC: Analog to Digital Converter

    2. DAC: An output stage that handles the reverse function (Digital to Audio Converter)

SAMPLE RATE

• The analog signal is sampled at a defined interval per second

  • Expressed in hertz (Hz)

  • Most Common: 44.1 kHz (CDs) & 48 kHz (Film/TV)

  • The lower the sample the rate, the more grain & garbly the texture is

NYQUIST THEOREM

• Reproducing an audio signal that captures the frequency range of human hearing (which is about 20 kHz, or 18-30 kHz) TO AVOID AILASING!

  • Laptop to replicate noise heard!

  • You need at least x2 (DOUBLE) the SAMPLE RATE to produce sounds for the humans (so… 20 × 2 = 40!)

  • Aliasing is a type of distortion that occurs when high-frequency components of a signal are misinterpreted as low-frequency components

BIT DEPTH

• The number of bits used during sampling

  • Bit too low, the audio will start to sound grainy or metallic (resulting in more square-wave type waveforms!)

  • “Bit-Crushing” → reducing the sample size! More degrading it is, “aylising”

ADC & DAC

• Both are used to send & receive data between devices

• EX: Voice calling on a cell phone 

  • Audio signals are analog (signal’s waveform)

  • When someone talks into the phone’s microphone, the phone has an ADC that converts the analog signal into digital so that the other phone on the other end can receive it!

  • Signal sent from phone → telephone tower → satellite → another telephone tower!

ADC (ANALOG TO DIGITAL CONVERTER)

• Device that takes analog signals & converts them to digital signals

  • Converts natural waveforms of analog into digital, binary bits

  • Analog signals that have a continuous sequence with continuous values

DAC (DIGITAL TO ANALOG CONVERTER)

BLOCK —> WAVE

• Device that takes analog signals and converts the signal from digital bits of data & converts it back to natural waveforms of an analog signal (so we can understand it!)

  • Opposite function of ADC but same clock source

  • Digital info from daw convertor into analog signal!

  • Enables sounds to be reproduced through loudspeakers/headphones

  • Can improve conversion of a sound

Pro Tools

• EDITING MODES

1. SLIP MODE

2. GRID MODE

3. SHUFFLE MODE

4. SPOT MODE

Pro Tools

• EDITING MODES

  • 1. SLIP MODE

• Allows you to manipulate audio/tracks without a grid, you can adjust it to ANY part of the pro tools, clips can freely move across timeline

Pro Tools

• EDITING MODES

  • 2. GRID MODE

• Allows you to manipulate Audio and MIDI with a “Musical” timing reference → combo of Tempo & Meter, grid appears so all editing tools will “snap” to the grid

• Has TWO modes

  (1) ABSOLUTE MODE (Blue):

  (2) RELATIVE MODE (Purple):

Pro Tools

• EDITING MODES

  • 2. GRID MODE

    • (1) ABSOLUTE MODE

• Moving any clip snaps the clip start to Grid boundaries If a clip’s start point falls between beats, and the Grid is set to 1/4 notes, dragging the clip will snap its start time to the nearest 1/4 note (the current absolute Grid value)

• Pro Tools operates in this mode by default, change it by clicking on the dropdown!

• But working in the wrong mode can have dramatic results with your timing

Pro Tools

• EDITING MODES

  • 2. GRID MODE

    • (2) RELATIVE MODE

• Clips can be moved by Grid (or Nudge) units

• If a clip’s start point falls between beats and the Grid is set to 1/4 notes, dragging the clip will be constrained to 1/4 notes, preserving the clip’s relative position to the nearest beat

  • Ideal mode for editing drums & song structure (timing & internal edits will remain intact when moving things around)

Pro Tools

• TABBING TO TRANSIENT

• In Pro Tools, click Alt+Tab to see the parts of a clip you cut that are space! (So you start off well)

Pro Tools

• EDITING GROUPS

• Pro Tools also has a helpful tool called “Edit Groups” where you can edit multiple tracks at the same time (saves time)

• Located below the Tracks list

• You can disable ALL groups by clicking “Suspend all Groups” or pressing shift G

• You can also modify each group by right clicking the group you want and clicking modify

Pro Tools

• ELASTIC AUDIO

• Pro Tools offers elastic properties!

• Includes pitch shifting

• Trimmer Tool set to TCE Mode, audio now can be extended/stretched to make the audio sound more “interesting”

Pro Tools

• ELASTIC AUDIO

  • TYPES OF AUDIO

1. POLYPHONIC

2. RHYTHMIC

3. MONOPHONIC

4. VARISPEED

Pro Tools

• ELASTIC AUDIO

  • TYPES OF AUDIO:

    [1] POLYPHONIC

• Audio with different simultaneous pitches such as piano, guitar, entire mixes

Pro Tools

• ELASTIC AUDIO

  • TYPES OF AUDIO:
    [2] RHYTHMIC

• Audio with percussive elements such as Drums, Percussion

Pro Tools

• ELASTIC AUDIO

  • TYPES OF AUDIO:
    [3] MONOPHONIC

• Audio with single notes at a time such as bass, vocals, trumpet etc.

Pro Tools

• ELASTIC AUDIO

  • TYPES OF AUDIO:
    [4] VARISPEED

• Instead of keeping the pitch intact, Protools will lower or increase the audio speed to fit the clip boundary

• This is the same concept as speeding up or slowing down a tape