1. Indoor & Outdoor Acoustic Sounds – A Deeper Understanding
Beyond the basics
Indoor Acoustics
The Principles of Sound and Acoustics
Sound is the apparent vibration of air resulting from the vibration of a sound source (e.g.
guitar sound board, hair dryer, etc). We can describe such regular vibration in terms of the
sum of simpler vibrations (harmonics). In other words any periodic oscillation and hence
resulting waveform can be described in terms of the sum of its harmonics. Each harmonic
being a simple sine wave (often called a pure tone) with it’s own respective frequency and
amplitude.
Studio-based Acoustics
When you're trying to set up a studio on a limited budget, it's all too easy to concentrate on
buying equipment rather than spending your hard-earned cash on things that don't make a
sound. A little money spent treating the room in which your studio is based, however, can
often be a better investment. A lot of people find out too late that the acoustics of their
chosen room cause problems, either by colouring their recordings, distorting their
monitoring perspective or leaking sound.
Live Room
The typical recording studio consists of a room called the "studio" or "live room", where
instrumentalists and vocalists perform; and the "control room", which houses the
professional audio equipment for either analogue or digital recording, routing and
manipulating the sound. Often, there will be smaller rooms called "isolation booths" present
to accommodate loud instruments such as drums or electric guitar, to keep these sounds
from being audible to the microphones that are capturing the sounds from other
instruments, or to provide "drier" rooms for recording vocals or quieter acoustic
instruments.
Dead Room
A lot of studios pride themselves in having a ‘dead’ room. What does this that mean?

2. It’s free and clear of ambient noise
It has enough treatments in it to soak up any sound made in the room (so as not to
hear an echo).
When recording at home, sometimes it’s hard to get a dead room. Heating/AC vents,
windows, neighbors, etc. all contribute to those ambient noises that you’re trying to keep
out of your recording. You can also be the culprit with loose clothing, watches, a squeaky
chair, computer fan, and even things like moving papers around.
Surface types and properties;
When a sound wave meets an obstacle, some of the sound is reflected back from the
front surface and some of the sound passes into the obstacle material, where it is
absorbed or transmitted through the material. Reflection and absorption are dependent
on the wavelength of the sound. The percentage of the sound transmitted through an
obstacle depends on how much sound is reflected and how much is absorbed. We are
assuming that the obstacle is relatively large, such that no sound passes around the
edges.
When a sound wave in air reaches the surface of another material, some of the sound is
reflected off the surface, while the rest of it goes into the material. For example, when
sound hits a wall, some is reflected and some passes into the wall.
If the surface that the sound wave hits is relatively smooth, more sound will be reflected
than if the surface is rough. For example, more sound will be reflected from a smooth
wall made of mud than a pile of dirt. The reason is that the rough or porous surface
allows for many internal reflections, resulting in more absorption and less reflection.
Some materials absorb sound more than others. Drapes and ceiling tiles are used to
absorb unwanted sound and eliminate echoes. Music recording studios use sound
absorbing materials on their walls to eliminate any undesired or outside sounds, when
recording a song.
Reverberation;
Reverberation is the persistence of sound in a particular space after the original sound is
removed. Originally, the studio recordings were performed through the microphone quite
remote from the sound source. This microphone, like the human ear, received the sound
waves reflected from the walls of the studio room, and enrolled it into the recording. In the
way the natural reverb of the studio was preserved in the recording. The effect was even
more pronounced, when they began to use several microphones, respectively mixed with
each other, this way even better results could be achieved.

3. Sound proofing;
Soundproofing is any means of reducing the sound pressure with respect to a specified
sound source and receptor. There are several basic approaches to reducing sound:
increasing the distance between source and receiver, using noise barriers to reflect or
absorb the energy of the sound waves, using damping structures such as sound baffles, or
using active antinomies sound generators. Since the early 1970s, it has become common
practice in the United States and other industrialized countries to engineer noise barriers
along major highways to protect adjacent residents from intruding roadway noise. The
technology exists to predict accurately the optimum geometry for the noise barrier design.
Noise barriers may be constructed of wood, masonry, earth or a combination thereof. An
anechoic chamber (an-echoic meaning non-echoing or echo-free) is a room designed to stop
reflections of either sound or electromagnetic waves. They are also insulated from exterior
sources of noise. The combination of both aspects means they simulate a quiet open-space
of infinite dimension, which is useful when exterior influences would otherwise give false
results. Anechoic chambers were originally used in the context of acoustics (sound waves) to
minimize the reflections of a room. More recently, rooms designed to reduce reflection and
external noises in radio frequencies have been used to test antennas, radars, or
electromagnetic interference.
Outdoor Acoustics
Sound bites; background atmosphere;
A sound bite is a short clip of speech or music extracted from a longer piece of audio. It is
often used to promote or exemplify the full length piece. It may also be abbreviated as SOT.
Before the actual term "sound bite" had been coined, Mark Twain described the concept as
"a minimum of sound to a maximum of sense." It is characterized by a short phrase or
sentence that deftly captures the essence of what the speaker is trying to say. Such key
moments in dialogue (or monologue) stand out more strongly in the audience's memory
and thus become the best "taste" of the larger message or conversation. As the context of
what is being said is missing, the insertion of sound bites into news broadcasts or
documentaries is open to manipulation and thus requires a very high degree of journalistic
ethics. According to the Code of Ethics of the Society of Professional Journalists, journalists
should "make certain that headlines, news teases and promotional material, photos, video,
audio, graphics, sound bites and quotations do not misrepresent. They should not
oversimplify or highlight incidents out of context."
In filmmaking and television production presence (or room tone) is the "silence" recorded at
a location or space when no dialogue is spoken. This term is often confused with ambience.
Every location has a distinct presence created by the position of the microphone in relation
to the space boundaries. A microphone placed in two different locations of the same room
will produce two different presences. This is because of the unique spatial relationship
between the microphone and boundaries such as walls, ceiling, floor and other objects in
the room. Presence is recorded during the production stage of filmmaking. It is used to help

4. create the film sound track, where presence may be intercut with dialogue to smooth out
any sound edit points. The sound track "going dead" would be perceived by the audience
not as silence, but as a failure of the sound system. For this reason presence is normally
recorded - like dialogue - in mono, with the microphone in the same position and
orientation as the original dialogue recording. In the sound edit, presence occupies the
same track as the dialogue to which it applies.
Unwanted noise;
A Noise Gate or gate is an electronic device or software that is used to control the volume of
an audio signal. In its most simple form, a noise gate allows a signal to pass through only
when it is above a set threshold: the gate is 'open'. If the signal falls below the threshold no
signal is allowed to pass (or the signal is substantially attenuated): the gate is 'closed'. A
noise gate is used when the level of the 'signal' is above the level of the 'noise'. The
threshold is set above the level of the 'noise' and so when there is no 'signal' the gate is
closed. A noise gate does not remove noise from the signal. When the gate is open both the
signal and the noise will pass through.
They are commonly used in the recording studio and sound reinforcement. Rock musicians
may also use small portable units to control unwanted noise from their amplification
systems. Band-limited noise gates are also used to eliminate background noise from audio
recordings by eliminating frequency bands that contain only static.
Unwanted Ambience;
As you edit dialogue, you’ll often need to cut out pieces of audio that you don’t want in the
sequence. For example, the director may have given directions in between an actor’s lines,
or the sound recordist might have bumped into something while shooting on location for a
documentary. As long as there’s no dialogue happening at the same time, it’s pretty easy to
cut out unwanted sounds. If you simply delete the sound, however, you’ll be left with a gap
in your audio that sounds artificial. Since there’s always a low level of background noise,

5. known as room tone, in any recording, a moment of complete silence is jarring. In order to
edit out unwanted sections of audio without creating obvious gaps, it’s common practice to
record a certain amount of room tone during a shoot. The recordist simply has everyone
stand quietly for thirty seconds or so, and records the ambient sound of the room. If you’ve
recorded some room tone during your shoot, you can capture it so that, as you edit, you
have a long piece of “silence” that you can edit in whenever you need to cover a gap in the
location audio. If, for some reason, room tone was not captured for a particular scene, but
you have a gap you need to fill, you can try to copy a section from another clip in the same
scene that has a pause in the dialogue, and paste it to fill the gap. If you have no pauses that
are long enough to cover your gap, you can try to copy and paste a short pause multiple
times. But there’s a chance that it will end up sounding like a loop, which will be too
noticeable. In this case, you can use the following method to obtain a long section of room
tone from a short copied pause in the dialogue.
Wind noise (Refer to your location recordings and essay)
Recorded wind noise is a blatant sign of an amateur. With just a little know-how, it's entirely
possible to achieve good quality audio recordings, even with consumer-quality equipment.
To prevent wind noise, all you need to do is prevent wind from striking the microphone's
sound element. The black foam windscreens that come with most microphones helps to
reduce noise caused by mild air movement indoors. Foam windscreens are made from
special open-cell foam. "Open cell" means you can blow air through the foam's cells. These
cells create an airspace around the microphone, dampening the effects of air movement,
while still allowing sound waves to reach the mics sound element. Foam windscreens are
usually fine for use in barely perceivable wind, and they certainly do a great job of
protecting your microphone from damage, but the surface of a foam screen is just too
dense to adequately dampen the strike of wind against your microphone the way a fur
windscreen does.
Fur windscreens
Fur windscreens, when used over a foam windscreen, provide maximum wind noise
reduction. A fur windscreen's synthetic hairs, being a soft and pliable material, soften the

6. wind's effect on the mic. The fur breaks up the wind and dampens (quiets) it. Think of
striking a solid surface, like a door, with your hand. It would be fairly loud, almost drum-like
sound. Now imagine knocking on someone's door that is covered in a soft plush fabric like
the synthetic fur. Instead of a reverberating beat, your knock would be silenced by the
sound absorbing outer layer of fur.