SOUND BASICS
What is sound?
Sound is vibrations that travel through the air or other mediums { liquid, solid}. These vibrations arrive at the ear and
are interpreted as sound . A sound event , such as handclap , disturbs the air molecules. Like the effect of dropping a
rock in a pond, the air molecules create waves of movement in the air that radiate from the point of the disturbance .
These vibrations are called “ sound pressure waves “.
Sound waves
There are two parts to a sound wave; <a compression and rarefaction >. A compression occurs when the air
molecules are forced together. and a rarefaction occurs when the air molecules move away from each other.
When there is neither a compression or a rarefaction, the air molecules are at rest. This known as silence. Si-
lence is like a still pond. There are no waves. When a rock is dropped in the pond, the water molecule are
forced to displace. The point of impact forces the water down and causes the surrounding water molecules to
rise. This the creation of the wave. In an effort to find to find rest again , the water molecules ripple in waves
away from the source of impact. Compressions occur when the water rises above the surface. Rarefactions
occur when the water sinks below the surface. A wave cycle consists of one compression and one rarefaction
Compression Wave length
[crest] Positive Amplitude
Point of Rest
[Zero line]
Negative
Rarefaction Amplitude Wave cycle
[ trough ]
FUNDAMENTALS OF FILM SOUND
Acoustic properties
The fundamental acoustic properties of film sound; frequency , amplitude and timbre. They
interact to define the overall sonic texture of film . At the most basic level , these three acous-
tic factors enable us to distinguish the various sounds in a film. For example , recognize dif-
ferent character's voices.
i. Frequency
One of the ways sound wave are measured . Frequency is also known as pitch, refers to the number
of complete wave cycles [ one compression and one rarefaction ] that occur in a second . Frequency
is measured in hertz [ Hz]. The mor e wave cycles the higher the fr equency will be. A sound that
consists of 100 wave cycles per second is written as 100Hz. A sound that consists of 1000 cycles per
second is written as 1 kHz [ K is for “ kilo”, or 1000 Hz ]
The hearing range of the human ear is 20Hz — 20 kHz. This is a textbook number . In r eal
world , the hearing response for the average male is 40Hz — 18 kHz. Woman have a slightly better
hearing response for higher frequencies than men do. Cats have a hearing range of 45 Hz — 64 kHz.
The average frequency range for human speech is 100 Hz — 3 kHz , although har monics can far
exceed this range , some males can produce speech frequencies as low as 60 Hz. Higher frequencies
are perceived as being higher in pitch. Low frequencies are perceived as being lower in pitch .
Frequency
Low frequency . High frequency
There are three main ranges of frequencies within the audible frequency range;
Low range or “ low End “: 20 Hz — 200 hz
Mid - range or “ Mids” 200 Hz — 5 kHz
High - range or “ high End “ : 5 kHz — 20 kHz
Audio signal chain
Microphone cable audio recorder
Single system Double system
Video and audio already synced video audio codec ; if you don’t have a camera with professional input
16 bit us an audio recorder
48 kHz
Uncompressed
Sampling rate [ kHz ]
11 kHz low quality , internet audio
44.1 kHz , CD quality
48 kHz , digital video audio
Audio cable
Analog cables
Un balanced and balance
Un balanced is the cheapest
Draw the cable!
Ground in white . Wave drawled
Hot in red
Balanced
Draw the cable
Hot in red waves ; red wave
Ground in white
Cold in green wave; green
Types of mics
Shot gun mic
Rod ntg
Wireless systems ; but expensive , battery hog
Head phone
Never forget headphone
