This document discusses the physics of sound waves including their generation, propagation through different mediums, and measurement. It covers topics such as wavelength, frequency, amplitude, pitch, loudness, and the human range of hearing. It also discusses how sound is measured scientifically and concepts like interference, resonance, absorption, and reverberation in rooms.

1. Physics of Sound
Part 1
Sound waves
How they are generated and
travel

2. Sound Waves
 Generation and Propagation
 Sound wave = changes in pressure caused by
vibrating object
 Compression = High pressure
 Rarefaction = Low pressure
 Sound needs a medium to “vibrate”
 Usually air, but could be anything
 Speed of sound depends upon the medium
Air = 1130 ft/sec Water = 5000 ft/sec Steel = 13000 ft/sec

3. Measuring sound waves
 Sound waves are longitudinal waves
 Vibrating object compresses the air around it.
 Pushes air away leaving an area of low pressure
 Vibrating object then compresses more air to create a
“chain”

4. Measuring methods
Cycle
 A single push and pull of the vibrating object
 One are of compression followed by one area of
rarefaction
 An initial increase in atmospheric pressure from the
norm, followed by a drop below the norm and then a
return to normal
 Mathematically displayed by a sine curve
 Pressure on Y axis
 Time on X axis

5. Measuring methods
Period (T) and Frequency (f)
 Period - The time it takes to create one cycle
 Frequency - The number of cycles in one second
1
f
T
=
 Measured in Hertz (Hz) or cycles per second

6. Measuring methods
Example
It takes ¼ sec to create one cycle. What is
the sound wave’s frequency?
1
4 cycles per second
.25
f = =

7. Measuring methods
 Frequency will determine pitch
 High frequency = high pitch
 Low frequency = low pitch
 Octave – a doubling of halving of the
frequency

8. Measuring methods
 Human hearing range
 Low range between 15 to 30 Hz
 With enough power lower than 15 Hz can be felt, but
not heard as “sound”
 High range varies with age and gender
 Women - up to 20 kHz
 Men – between 15 to 18 kHz
 High frequency range will lower with exposure to high
levels of sound and age

9. Tuning
 Traditional orchestra would tune First Chair Violin A first.
 Remaining instruments would tune relative to that
 A above middle C was tuned to about 420 Hz
 As halls grew larger it was found to be desirable to tune sharper
 1939 A was established to be 440 Hz
 Corresponds to the 49th
key on a full size piano
 Tuning is not a science. The relative frequency difference is
what is important

10. Measuring methods
Wavelength
 The distance from one area of compression
to the next or one area of rarefaction to the
next v
f
λ =
l=wave length
V = velocity of sound in medium
usually 1130 ft/sec
f = frequency

11. Measuring methods
 Amplitude
 How high the pressure goes above and below
normal atmospheric pressure
 Corresponds to how loud the sound is
 “loudness” is relative to frequency and dependant
on the listener.

12. Timber and Harmonics
 Harmonics – multiples of a base frequency
 Timber – the characteristics of a particular sound or
instrument
 Different harmonics combined in different levels

13. Physics of Sound
Part 2
Basic Acoustics
Inverse square law
Reinforcement/cancellation

14. Interference
 Phase
 measurement of where the amplitude of a wave is
relative to another wave
 A cycle can start at any point in a waveform
 Two waves with the same frequency can start at
different times
 Measured as an angle in degrees
 Related to the sine wave representation of the wave

15. Interference
 Constructive of
destructive interference
 Waveforms will add by
summing their signed
amplitude at each instant
in time

16. Beats
 Happens when two
slightly different
frequencies interfere
 Often used in tuning

17. Standing waves
 When sound waves bounce off
of obstructions, they can
interfere with themselves
 Tends to reinforce some
frequencies and attenuate
others
 Prevented by using
 Non- Parallel walls, ceilings
 Convex surfaces
 Multi-level ceiling sections

18. Reverberance (Reverb)
 Consisting of multiple, blended sound images caused by
reflections from walls, ceilings and other structures which do not
absorb sound
 NOT echo
 Echo consists of individual, non-blended sound images
 Reverb time is related to
 The time it takes for a sound to reduce to an inaudible level
 Loudness of sound relative to background noise
 Ratio of loudness of reverberant to direct sound
 Short reverb time (less than 1.5 sec) is better for speech or
drama
 Long reverb time (more than 1.5 sec.) is better for music

19. Absorption
 Controlling reflections can reduce or increase reverb
time
 Air tends to absorb frequencies above 2K Hz
 Sight line obstructions
 Frequencies above 10 kHz tend to not bend around
corners well or other obstructions
 l=1.3 inches for 10 kHz tone
 Frequencies below 1kHz do very well
 l=5.65 feet for 200 Hz tone
 Specialists are often hired to “tune” a space
acoustically

20. Acoustic attributes
 Defined by Leo Beranek after a 6 year study
of 54 concert halls
 Used to define acoustic properties in terms
that other trained professionals can
understand

21. Acoustic attributes
 Intimacy – Indicates the size of a room
 How it sounds to the listener, not actual size
 Determined by the initial-time-delay-gap (ITDG)
 Interval between the sound that arrives directly at the
ear and the first reflection
 Usually considered to be the most important
attribute

22. Acoustic attributes
 Liveness
 Related to Reverberance
 Room size is related
 More reflections is live. Less reflections is dry or
dead
 Warmth
 More low frequency sound relative to mid
frequency
 Too much low frequency sound is said to be
“Boomy”

23. Acoustic attributes
 Loudness of direct sound
 Inverse square law
 Loudness of sound will decrease by one quarter
every time the distance from the source is
doubled
 Definition or Clarity
 Good definition when sound is clear.
 Related to intimacy, liveness, loudness of direct
and reverberant sound

24. Acoustic attributes
 Brilliance
 A hall that has liveness, clarity and intimacy
 Diffusion
 Relates to the orientation of reverberant sound
 Where is the reflected sound coming from
 It is preferable to have reverb sound coming from
all directions

25. Intensity
 Like pitch, loudness is a sensation in the
consciousness of a listener
 To produce a sound twice as loud requires 10
times the power
 Inverse square law
 Sound level is reduced by a factor of the square
of the distance away from the source
 If you move double the distance from the source, the
sound intensity will by one quarter

26. Intensity
 Intensity is a measurable quantity
 SPL – Sound Pressure Level
 dB – deciBel
 A system of measuring a ratio between two powers
 1dB change – Imperceptible change
 3dB change – Barely perceptible
 5dB change – Clearly noticeable
 10dB change – About twice as loud
 20dB change – About four times as loud

27. dB SPL Sound
150 dB Jet engine at 1m
140 dB Rock and Roll stack at 1m
130 dB Thunderclap, Air Raid Siren 1 Meter
120 dB Jet takeoff (200 ft)
110 dB Rock Concert
100 dB Train passing up close
90 dB Heavy traffic
80 dB Hair Dryer
70 dB City street
60 dB Noisy bar or restaurant
50 dB Open plan office environment
40 dB Normal conversation level
30 dB Library, Soft Whisper (5 Meter)
20 dB Quiet domestic environment
10 dB Broadcasting Studio, Rustling Leaves
0 dB Threshold of hearing in young adult

29. Sound Envelope
 Listener does not hear individual cycles of sound waves
 Attack – Time it takes for sound to rise from nothing to its
greatest intensity. Usually short.
 Decay – Time it takes for a sound to fall from its attack level to its
sustaining level. Decay time is usually short
 Sustain – The time during which the initial vibrating source
continues to supply energy to the sound. Usually perceived as
the duration and intensity of the sound
 Release – Time it takes for the sound to drop from its sustain
level to inaudibility after vibrating object stops supplying energy

30. Sound Design
 How, what and why of a show

31. Interaction of Sound
with other Show Elements
 Script
Identification of motivational cues - sounds listed in
the script (cues that actors react to)
Identification of environmental cue opportunities –
locations, time of day, season, era,
Identification of emotional cue opportunities – What
do you want to say about actor, situation. . .

32. Interaction of Sound
with other Show Elements
 Acting
Collaborate on what is “heard” on stage - Actors
need to understand what sounds are part of the
physical environment shared with the set and props.
Some sounds are there for them to react to (Motivational)
Some sounds need to be originated by a performer’s
action (ring a bell, turn on a radio, etc...)
Monitoring of stage action to off-stage locations
Placement of wireless mics and stage monitoring /
fold back

33. Interaction of Sound
with other Show Elements
 Costumes
Musicals – wireless mics that need to be
accommodated within costumes and hair
 Scenic
Location of on-stage devices (speakers, mics)
Collaboration on scene shifts (needs/opportunities to
cover transitions using sound cues – “Functional”
sound cues)
Identification of cues that support each other (sound
used to reinforce scenic element that would normally
make noise (car, train station, rain, etc. . .)

34. Interaction of Sound
with other Show Elements
 Props
“Active” on-stage devices that may be props
 Lights
Identification of cues that support each other
Thunder and lightning,
Day time or night time,
Lights used to represent outdoors and other items/times
that would normally have a recognizable sound associated
with it.
Identification of transitions where cues should go
together

35. Interaction of Sound
with other Show Elements
 Music direction
Vocal reinforcement (micing)
Music reinforcement (micing, direct feeds and
mixing)
Vocal/music monitoring for performers and/or band
 Choreography
Music cues
Reinforcement of foot fall (Mic cues for tap dancing)
Music monitoring for dancers

36. Interaction of Sound
with Other Show Elements
 Stage Management
Cueing
Monitoring of stage action to booth
Intercom systems

37. Use of Sound in the Theatre
What Audience Hears – Company Hears
 Elements that are part of the show
 What an audience hears.
Cues, Aural Reinforcement
 Support for the Overall Production
 What the company hears
Monitoring, Communications
Recording

38. Use of Sound in the Theatre
What Audience Hears – Company Hears
 Sound Cues - “created” sounds that
advance the story
Sound effects, music transitions and underscoring.
Produced / reproduced through mechanical or
electronic means
Mechanical – real sounds (sheet metal for thunder, crash
box for breaking glass, ½ coconuts for horse galloping,
actors making bird calls)
Also called practical
Electronic reproduction
Sounds stored as signals on CDs, Minidisks,
computer files

39. Use of Sound in the Theatre
What Audience Hears – Company Hears
 Reinforcement of aural elements of
production
 Mic cues for vocal and musical performance
 Orchestra Mics
 Instrument direct feeds

40. Use of Sound in the Theatre
What Audience Hears – Company Hears
 Monitoring – Providing performers and members of the
company a portion of the sound from the performance to assist
with their performance.
 Stage monitors for singers to hear the band – and
themselves – Fold back
 Pit monitors for band to hear vocals – and themselves
 House monitoring for crew positions, back stage and
dressing rooms so company can hear “what’s going on”

41. Use of Sound in the Theatre
What Audience Hears – Company Hears
 Communications
Intercoms for cueing and communications among the
company
 Recording
Live feeds of performance for film, video and audio
recording

42. Paper work, paper work, paper
work….
CUE DEVICE INPUT CH LEVEL DEVICE OUTPUT CH LEVEL FADE TIME NOTES
SUFFOLK COUNTY COMMUNITY COLLEGE
SOUND CUE SHEET
Show:_________________________________________ Sem / Year _____/_____
Page _____ of _____

43. Paper work, paper work, paper
work….
CUE # Sound Cue Placement PG. Type Location
A Preshow music At house opening 7 Called Cluster / BOH
B Preshow announcement with house to half 7 Called Cluster
C Preshow fade with blackout 7 Called Cluster / BOH
D Narrator with lights up 7 Called Cluster
E "Loser" with lights up 9 Called USC
F music cut Chuck: "…the fuck!" 9 Called USC
G Awesome sound Agnes: "Go." 13 Called cluster
H Mission Impossible theme Agnes: "…the intro music!" 14 Called cluster
I music cut ??? 14 Called cluster
J Narrator TOS 18 Called cluster
K T.V. with lights up 18 Called USC
L T.V. fade Tilly: "…not good at all." 19 Called USC
M magic Agnes: "What are you doing?" 23 Called cluster
N fight music Chuck: "…what happens next - " 24 Called cluster
O music cut end of fight 24 Called cluster
P Narrator into LL Cool J Lilith: "…kicketh some ass." 26 Called cluster
R "Waterfalls" with lights up 28 Called cluster
S Voice Over Tilly: "…Let's do this!" 29 Called cluster
T magic missle with spell 29 Called cluster
U Farrah explodes Farrah: "Oh no." 29 Called cluster
V Cheerleader enterance Agnes: "…would be a bad thing, right?" 34 Called Cluster
W music cut 34 Called Cluster
X cube eats Steve: "…oh neat, a jello mold!" 47 Called USC
Y cube transforms Tilly: "…call it Miles." 49 Called Cluster
Z "Gonna Make you Sweat" Chuck: "…Cheerleaders!!!" 59 Called Cluster
AA Footsteps with blackout 69 Called SL
BB Tiamat Roar 69 Called SL
CC Tiamat fight 69 Called SL
DD Curtain call with lights up 71 Called Cluster

44. Paper work, paper work, paper
work….

45. For Next Class
 Read
 The Spaghetti Factor!, Coleman
 Patches and Facility Panels, Coleman
 Soldering and Soldering 2 PDF
Study for Quiz 1