3. The Sound Wave
Four Parts
Compression – most pressure
Rarefaction – least pressure
Amplitude = volume/loudness
Wavelength = pitch/frequency
4. Pitch & Frequency
Pitch = relative highness or lowness of sound
Frequency = number of cycles per second
One cycle = 1 compression + 1 rarefaction
Measured in Hertz (Hz) and Kilohertz (kHz)
100 cycles per second = 100 Hz
1000 Hz = 1kHz
5. The Audio Range
Normal audio range utilized in professional
music/audio applications?
20 Hz ~ 20 kHz
Normal hearing range?
35 Hz ~ 16 kHz
By age 50, most people only hear up to 10 kHz
6. Musical Pitch
Middle-C = 261.63 Hz
A440 = 440 Hz
A = only whole numbers on the piano
Octave Identification
Middle-C = C4 (traditionally)
C3 in Pro Tools and Logic; C5 in FL Studio
8. Octave
Up an octave = frequency doubles
Down an octave = frequency halves
9. Frequency Spectrum
10 audible octaves in the audible frequency
spectrum
1st octave = 20-40 Hz
2nd octave = 40-80 Hz
3rd octave = 80-160 Hz
10th octave = 10,240-20,480 Hz
10. Phase
Digital audio waveforms can be in phase or out
of phase
Phase can be constructive or destructive
Measured in degrees
One cycle is equal to 360 degrees
11. Phase (cont.)
In phase waveforms = added amplitude, louder
volume
Out of phase (partially) = reduced amplitude
Out of phase (completely) = no sound
12. Timbre
Timbre = characteristic quality of a sound
Sine wave = pure tone with only 1 frequency
Most sound contains multiple frequencies
Sine wave does not exist from acoustical
instruments
13. Timbre (cont.)
Fundamental = bottom “core” frequency of a
sound
Partials = frequencies that exist above the
fundamental
Harmonics vs. Overtones
16. Acoustics
The science of a sound wave‟s behavior as it
travels through an acoustic environment
Generation
Transmission
Reception
Effects
17. Acoustical Sound
Unrecorded acoustical sound is omni-directional
Three dimensional – depth, width, height
Stereo sound = Lateral
Two dimensional = depth, width
How do we create depth in a stereo recording?
18. Direct vs. Indirect Sound
Direct sound = reaches the listener first; comes
directly from the sound source
Indirect sound = reflects off of one or more
surfaces before reaching the listener
Early reflections
Reverberation (Reverb)
19. Studio Design
Recording Stage/Booth
Acoustic treatment must be appropriate to the music
being performed
Isolation Booth (Iso Booth)
Little, or no, reverb
Control Room
Acoustic treatment must be appropriate for the
mixing/mastering/monitoring experience
21. Reflection
The angle of incidence is equal to the angle of
reflectance
Rooms with flat parallel walls are more prone to
unwanted reflections
Change the angle of one or more walls to
compensate
22. Absorption
Sound is almost never completely absorbed;
usually absorbed and reflected
Types of Absorbers
Porous/Foam absorbers
Foam corner blocks (aka „bass traps‟)
Diaphragmatic/Helmholtz absorber
27. Monitoring Symmetry & Tips
Speakers should be equal distance from
walls and corners at an equilateral
triangle to the monitoring position
Avoid putting monitor backs too close to
walls (if your room is big enough)
Back/side wall diffusers work well to
scatter reflections
If your room is too small, put diffusers
behind the monitors
Square room = bad = more resonances
28. Monitor Vibrations
AuralexMoPads
Reduce vibrations
from setting monitors
directly on desks
Angle monitors down
if desk is too high
29. Why all the fuss?
Why all the fuss about proper acoustic treatment?
What‟s wrong with my bedroom/apartment?
All sounds are a product of their environment
Every mix will sound different based upon the proper (or
improper) acoustic treatment of a room
Better acoustics = more accurate mix = better mix = less
work for you
30.
31. Analog Recordings
Signal is continuous
Voltage running from a mic to the Mbox
Mbox converts to a digital format
Time & Level = Wavelength & Amplitude
32. Digital Recordings
Numerical representation of analog sound
signal‟s actual frequencies and amplitude
Sampling = number of discrete values taken per
second
Quantization = number of digital „levels‟ of
information
33. Sampling/Sample Rate
Number of samples taken per second
Some common sampling rates
32 kHz – broadcasting
44.1 kHz – Red Book CD format
48 kHz – digital video recorders / DVD-audio
96 kHz – DVD-audio
The higher the sampling rate, the higher the frequency
range
34. Bit Depth (Resolution)
Describes the number of bits of information
recorded for each sample
CD = 16-bit
DVD = up to 24-bit
The higher the bit depth, the higher the dynamic
range
More mix “head room”
Does not affect frequency range
35. Audio Quantization & Binary Code
The bit depth determines the number of bits of
information taken per sample
16-bit signal = 216 = 2x2x2x2x2x2…. (16 times)
216 = 65,536 possible combinations between
0000 0000 0000 0000 and
1111 1111 1111 1111
36. AQ & BC (cont.)
Bit depth
determines the
number of
“Quantization
Levels/Layers”
Example of a
Sine Wave at a
2-bit resolution
37. AD & DA Conversion
ADC = analog-to-digital converter
DAC = digital-to-analog converter
What converts a signal from analog to digital can be a
number of devices:
Digital mixer with mic/line inputs
Audio interface = Mbox/002
Sound card in the computer
CD/MP3 player
38. Digital Audio Workstations
Digital Audio Workstations (DAW)
Record, edit, and playback
Computer-based DAW (ex: Mac + Mbox + Protools)
Processing, mixing, and manipulation handled by the
computer
Sound card or audio interface needed to input/output
audio
Integrated DAW (ex: BOSS BR-1600 CD)
Software, console, and control surface are an all-in-one
unit
40. Uncompressed Files in Practice
WAV and AIFF (uncompressed) are the file types
that are generally worked with
They are “Flexible” file types that can handle any
Sample Rate / Bit Depth combination
Audio Recording software does NOT directly
record to compressed formats
41. DAWs& Audio Data Rate
Audio Data Rate = defines the flow/size of data
within an uncompressed format (WAV/AIFF)
AKA „Bit Rate‟
Red Book CD = 16-bit x 44,100 Hz
705,600 bits of information per SECOND
42. DAWs and Sample Rate
Most DAWs can support files with multiple bit
depths
DAWs cannot run multiple files with different
sample rates simultaneously
The sample rate of the project must match the
sample rate of the files in the project, if not, the
files will not play at the correct playback speed
43. Sample Rate &Nyquist
As said before:
The higher the sample rate, the higher the frequency range
of an audio recording
Nyquist Frequency
Half of the sample rate
Determines the highest frequency that can be accurately
reproduced in an audio recording
CD Sample Rate = 44,100 Hz
Nyquist of 22,050 Hz
