Download Sound Waves Resonance, Frequency and the Musical Scale

Sound Waves
Resonance, Frequency
and the Musical Scale
www.miqel.com/.../vibrational-truth.html <http://www.miqel.com/jazz_music_heart/vibrational-truth.html>
Natural Frequency
- All objects have a natural frequency at which they vibrate or
resonate when struck, plucked strummed etc.
-Each natural frequency is a standing wave.
-An object's natural frequency is the frequency that allows it
to vibrates with the least input of energy.
Mythbusters Shattered Glass
http://www.youtube.com/watch?v=O9FrMkhQoA4&safe=active
Natural Frequency versus Resonance
Natural Frequency - the frequency an object will tend to vibrate at
when struck or disturbed.
Forced Vibration - the tendency of one vibrating object to force
another CONNECTED object to vibrate. This causes an increase in
amplitude.
https://www.youtube.com/watch?v=wvJAgrUBF4w
Resonance - when one vibrating object causes another to vibrate
without directly touching the second object.
Beat Frequency
When two (or more) sound waves of nearly equal frequency are
played at the same time, the constructive and destructive
interference has a predictable pattern of large and small
amplitudes.
The Beat Frequency is
Δf =Ιf2 - f1 Ι
Humans can hear a beat frequency of less than 7 Hz.
https://www.youtube.com/watch?v=aCocQa2Bcuc
Note: The sound waves are shown as transverse (or sine waves)
for ease of drawing. Sound waves are longitudinal waves.
Pitch verses Frequency
-Frequency is the number of cycles/second.
-Pitch is the perceived frequency of a sound.
ie. a musician hears 256 Hz and 512 Hz as the same pitch or note. (in
this case a C ).
http://www.virtualpiano.net/
Musical Scale
European tradition divides the musical Octave into 12 notes.
The 12th note is the same note as the first only an octave higher.
Other musical systems divide the scale into between 42 and 360
notes. In each system the last note of the scale has twice the
frequency of the first note.
The Ratio of Frequencies for octaves is:
2:1
Second Octave Frequency : First Octave Frequency
down 1 octave
up 1 octave
Example
Middle C = 256 Hz
C note 1 octave below =
A note is a single tone, pitch or frequency.
A doubling of the frequency of any note produces a higher note with the same pitch, as in
middle C and high C on a piano. This is known as an Octave.
Octaves go on forever above and below our musical scale, they are simply halving's or
doublings of frequency.
A chord is any two notes or pitches played simultaneously.
All chords produce certain sounds which are unique because whenever
two notes are played together, a third note or beat is also heard.
Musical Scale
The most basic scale is called the diatonic scale.
C
D
E
F
G
A
B
4
--
5
-4
4
6
---
5
5
---
C1
D1
6
6
Major Triad - a collection of three notes with frequencies in the
ratio
4: 5: 6
There are three triads in each octave.
Example 1
Middle C = 256 Hz
E note =
G note =
4: 5: 6 major triad
C:E:G
E =5
C 4
E = 5C
4
where C = 256 Hz
Example 2
C1 note = 512 Hz
A note =
F note =
http://www.ted.com/talks/yoav_medan_ultrasound_surgery_healing_without_cuts
Homework:
White booklet
Read pages 17-23
Complete questions
8-11 page 25
Pink Booklet
questions 1-5 pages 7 and 8