Audio Primer – Music For All Summer Symposium Clinic
The following are the “Cliffs Notes” from my clinic focused on Audio at the 2015 Music For All Summer Symposium:
In order to have sound to exist -what 3 things are needed?
1. Generation (Vibration)
2. Propagation (Medium)
3. Reception (Hearing/Philosophical) – If a tree falls in the forest and nothing/nobody is there to hear it did it make a sound?
Characteristics of sound:
The “Big Two”:
1. Pitch (Frequency)
2. Volume (Amplitude)
The Musician’s Two:
The Forgotten One:
*Typical representation of sound as a Sine Wave (Image: Wikimedia):
*Amplitude shows us loudness and horizontal length shows frequency.
Audio engineers use the term “frequency”, musicians use its synonym, “pitch”. Today’s pianos, guitars and various string instruments tune using the “Equal Temperament” adjustment system. Wind instruments, such as the trumpet, are naturally tuned to a pure system of intonation known as the temperament, “Just Intonation”. These two temperaments cause many of the intonation issues for wind players and are a root cause for “natural tuning” tendencies and adjustments that are made for wind players when playing with equally tempered instruments. Equal tempered instruments are often referred to as being tuned “equally well” for playing in each octave, but could also be considered tuned “equally bad” -a topic for another time.
Common Pitch Frequencies (Equal Temperament) of notes in Hertz (Hz):
C (middle) 261.63
Volume changes or “sound intensity changes” are noted in “Bels” or 10ths of Bels (decibels).
A typical dB chart for Sound Pressure Levels (SPL) would be:
120 dB Too Loud for anybody
110 dB The Threshold of Pain/Thunder at 300′
100 dB Riveting Machine at 5′
90 dB Big Truck at 20′
80 dB Lawn Mower at 10′
70 dB Average loud room
60 dB Normal Conversation at 5′
50 dB Average Office (non-noisy)
40 dB Quiet Room or Office
30 dB Very Quiet Room
20 dB Quiet Recording Studio
0 dB Threshold of Sound
Music related terms and dB:
fff 100-105 dB at Conductor’s Spot
ff 90-95 dB at Conductor’s Spot
f 80-90 dB at Conductor’s Spot
mf 75-80 dB at Conductor’s Spot
mp -60-70 dB at Conductor’s Spot
p 55-60 dB at conductor’s Spot
pp 50-55 dB at conductor’s Spot
ppp 45-50 dB at conductor’s Spot
1. a dB level without a distance is usually meaningless (inverse square law)
2. Inverse Square Law: Double the distance -drop the SPL by 6 dB (10x the distance approximately 20 dB loss)/Halve the distance -increase the SPL by 6 dB
3. Turning “up” the volume to what people typically hear as “twice as loud” is usually an increase of 3 to 6 dB. (related to the Inverse Square Law)
Additional Resource: Decibel Hearing Conversation Chart and Image
Definition: How a sound begins and ends.
*image snipped from Dolmetsch Online (full article at Dometsch here)
Timbre is simply how a “sound” appears aurally to each individual”. A trumpet sounds “brassy”, a clarinet sounds “reedy”, and a guitar sounds “twangy”, etc. Understanding how timbres are formed is a little more complex.
The Brief Primer on Harmonic Series:
Each complex sound (beyond a simple sine sound) is made up varying harmonics, as musicians we know this series as the Overtone Series -something easily explained by thinking about the partials on any brass instrument. Each of these partials have their own sound intensity based that differ from the normally dominant fundamental pitch being played –> The combination of all of the partials (or harmonically related notes of the series) create a compiled (or complex) wave form that we hear as differing timbres.
Image: Partials and note divisions
*image from Wikimedia Commons
The Hearing Process:
How do we hear?
Link to Video: Hearing Primer (YouTube)
The importance of protecting our hearing as musicians:
Three types of hearing loss:
3. Mixed (both)
Online Frequency Test: Link to the Audio Website
Audiograms and the Speech Banana:
Three Parts to any Audio System: (though we may have combined them into one single unit now!)
2. Signal Processing
Simple System Example:
Signal Processing: Amplification
Garbage In – Garbage Out!
Audio Editing Software:
Take your pick…dozens of selections -everybody has their favorite -they are all not equal, but most will do a decent job for two-track editing and ensemble needs.
Resource: Lifehacker on Audio Software
Making the connection between Octaves with EQ –> Double or Halve the Frequency to go to the next octave.
The importance of understanding frequency… Short of the original recording quality, nothing can enhance or take away from the sound of your audio like adjustments to Frequency.
More about recording audio:
Excellent, but older, resource for Audio for Music Educators
Shure: Audio for Music Educators (PDF)
Presonus: Music Education References